f9b08cf7f9fb498e286ed75af561f3bdfd7fbb36
110
Commits
| Author | SHA1 | Message | Date | |
|---|---|---|---|---|
  AnachronautandClaude Opus 5
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66be42d7bb |
A word the monitor does not know goes to the disk, not into the weeds
There was nothing at the end of the monitor's command list. An unrecognised word
fell off it and straight into sayPrompt - which is a ROUTINE, so its RET had
nothing of its own to return to and went wherever the Stack happened to be
pointing.
The user found it by typing a program's name at the monitor prompt, which is an
entirely reasonable thing to do: the monitor is a mode of the shell, so
everything the shell does is meant to work in it. What they got was a fault, and
before that a second prompt printed on top of the first - which is sayPrompt
doing exactly what it is for on its way past, and the tell that it had been
entered rather than called.
WHERE THAT RET WENT DECIDED HOW BAD IT WAS. Usually 0x0003, in the middle of
newLine, and the machine stopped on a byte that is not an instruction. Once it
was inside sbfsFormat, and the machine formatted the disk it had booted from -
the user's would not start again, and neither would mine, which is how I came to
have a reproduction before I had a diagnosis.
Pre-existing, and not recent: it is there at
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AnachronautandClaude Opus 5
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fd9c4c75f8 |
Tell the person where it hurts
A fault stopped the machine and printed a line to standard error. On a terminal that is a diagnosis. Behind a window it is a frozen picture and no reason at all, because the message went somewhere nobody was looking - the machine looked hung and was not. It had stopped, and said so invisibly. CosmOS catches all five faults now and says what happened on the screen, with the address, in red. A FAULT ENDS THE PROGRAM, NOT THE MACHINE. That is the answer to "carry on or start again", and it is not a compromise: a bare RETI from most of these meets the instruction that failed and fails again, so carrying on was never on offer. But the machine is almost never what is broken. Everything the shell puts back when a program exits - the Stack, its vectors, the drive, the working directory, the console, the screen - is exactly what wants putting back after one dies, so the handler sets a status and joins handleExit. You are back at the prompt, and the program is recorded as having STOPPED rather than finished, because saying "finished" under a red fault message would be the shell contradicting itself. A fault below where programs load is the system's own, and there is nothing to go back to. That one says so and stops. THE SCREEN GOES BACK TO A MODE TEXT CAN BE SEEN IN, and that is the part that matters rather than the part that is prettiest. A program that faulted in bitmap mode left the console with no text rows, so it draws nothing at all: the message would be perfectly correct and completely invisible, which is the one thing it must never be. Two palette entries go back for the same reason, since a program that wrote its own colours can leave every ink the same as every paper. Only the two the message needs, so the rest of what the program chose is left alone. Both halves are checked by looking at the PICTURE, because the serial line was never where the problem was. Crash blind ruins the palette and drops into bitmap mode before it faults; without the mode the screen comes back 320 by 200 with nothing on it, and without the palette it is the right size with the message present and unreadable. Each break loses the red on its own. Crash is also a program worth having: it breaks in whichever of the five ways you name, so a fault screen can be looked at without having written a bug first. Two things found on the way: The native assembler keeps its OWN copy of the reserved vector names, so it did not know NoHandler or NoDevice and built a cosmos.bin that differed from the host assembler's. Caught by native.sh, which is exactly the drift that test exists for. And cosmosMonitor had dead input. It assembles code into 0x8000 and runs it, and that code faults - which used to kill the machine, so everything after it in the file had never run. It runs now, and the recording grew by sixty lines of monitor session that had been unreachable since the day the fault was put there. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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4d976fc22a |
A program reading a line gets the editing too
osReadLine goes through the shell's editor now, so anything that asks the system for a line gets arrows, Home, End and Delete. The editor is a program, and a word typed with two letters the wrong way round can be put right without starting the line again. IT DOES NOT GET THE HISTORY, and that is the interesting half. Edit would otherwise fill the history with the text of somebody's document, and pressing Up in the middle of writing one would put "dir" into it. The history belongs to the thing whose lines are commands. Two entry points rather than a flag the caller sets first, so a caller cannot forget which it wanted. And the console is put back the way it was FOUND rather than the way the shell likes it. A program that had asked for key mode and then read a line through the system used to be handed back a console in line mode having asked for nothing of the sort. The status port reports all three things the control port can ask for, in the same order two bits along, so one shift turns what the console IS into what to write to make it that again. Which uncovered a real fault in the console. READING THE STATUS PORT WAS EATING A KEY: in line mode the poll consumed an arrow key and dropped it, so a program that looked and then asked for key mode - exactly what reading a line now does - found the first key it was reaching for already gone. A look must not consume what it cannot report, because the mode can change. It is held now and delivered as soon as something will take it. A blocking read still discards it, and must: that read IS the delivery, and a byte held there would be met again forever. Four recordings gained a program's echo, and cosmosEdit's went from "> : : : : > : : > 1: alpha" to a session you can read. VERIFIED THE SAME WAY AS BEFORE: with only the program side of the echo silenced, all 192 tests pass against the recordings as they were before this commit, so the echo is the whole of what changed. cosmosEditService is the new test and it checks both halves at once. Inside Edit, Left/Delete/Left puts "alpah" right. Up and Down do nothing there - were a program's line walking the shell's history, the next line would come out as the echo command from the top of the file instead of the word. And one press of Up back at the prompt finds the command typed before Edit was started, which is the proof that nothing the editor read went into the history at all. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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71f6e215f9 |
The shell remembers what was typed before it
Up walks back through the last eight lines and Down forward again. It exists only because the keys reach the system now: until A1 and A2 there was nothing to press Up at, and the line was assembled somewhere the shell could not see. A RING RATHER THAN A LIST. A ninth line pushes the oldest out by moving where the ring starts, not by moving any of the lines - so keeping a line costs a copy of that line and nothing else, however full the history is. Eight is a power of two, so which slot an entry lives in is an AND. The ISA had the awkward part already: A and B are a sixteen bit shift register, so one SHR with B empty turns a slot number into the offset of a 128 byte slot, high byte and low, ready for DPUW. A NINTH SLOT HOLDS WHAT WAS BEING TYPED when Up left it, and Down brings it back. Losing a half written line to a keypress is the sort of small rudeness that makes a thing unpleasant to use, and it costs one slot to avoid. An empty line is not kept, and neither is one the same as the line already at the top. The test proves the second by looking one further back: if a repeated command were kept twice, the line behind the newest would be the same line again. The redraw had to learn to rub out. One space was enough while the only thing that shortened a line was taking one character out of it; a recalled line replaces the whole of it, and a short line over a long one left the tail of the long one on screen looking like part of what you were typing. It now covers exactly what was lost - which turned out to be one space fewer than before in the cases that GREW, so two lines of cosmosEditKeys lost a trailing space that was never doing anything. Costs 1157 bytes of Data Memory, taking CosmOS to 6220 of the 8192 it has before a loaded program's data begins. Worth writing down: that is the budget, and this is the largest single thing in it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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81e544eb3d |
Load a program that has no data
A five instruction program that writes one port and exits has no Data Segment at all, and the loader stopped the machine dead on it. It asked the memory controller to move a segment of no bytes, and a length of zero asks for the whole 64K - which is the machine's rule, and a reasonable one, since two bytes cannot say 65536 and a transfer of nothing is not usually what anybody meant. It is exactly what was meant here. 64K did not fit, the controller refused, and the load stopped half done. ON A TERMINAL THAT PRINTS A FAULT WITH AN ADDRESS. Behind a window it is a frozen picture and no reason at all, which is how it was found and is a separate problem from this one. The header says how long each segment is, so the loader knows before it asks. Both bytes are already in hand, so the test costs one OR. Nothing is lost by skipping the transfer: a blit leaves the controller's addresses past whatever it touched, and a blit of nothing would have left them where they already are, which is where the vectors are read from next. Guarded for the code segment too. A program with no code is equally assemblable and would have stopped in exactly the same place. Mode.sbx is the fix's test and a program worth having on its own: forty columns or eighty, whichever the screen is not in, which is what a person wanting Snake drawn twice the size actually needs. Ten instructions and no data, deliberately - it prints its two digits a register at a time rather than from a string, so it stays the smallest shape a loadable program can take. Nothing else on that disk had ever been that shape, which is why nothing had ever tried it. Reported by the user, who wrote the program. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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736037462e |
The shell edits the line it is given
Three different things used to do this job, and which one you got depended on where the machine was running. On a terminal the host held the line and did the echoing and the backspacing; behind a window the console's own gatherer did it; from a file nothing did it at all. One job, three implementations, none of them in the system - which is why there was no way to move about in a line and nowhere for a history to live. So editLine does it. Key mode while a line is being read and line mode straight after, so nothing else in the system and no program calling osReadLine notices anything changed. Left and Right, Home and End, Backspace for the character before the cursor and Delete for the one under it, and anything typed goes in where the cursor is with the rest of the line moving along. Ctrl-D means the end of input again, on an empty line, because that was a thing the terminal did while it was holding the line and it is not holding it now. Same trade as the echoing. MOST KEYSTROKES DRAW NOTHING BUT THEMSELVES. A character typed at the end of a line needs no cursor moved: printing it is the whole change, and a backspace there is three ordinary bytes. That matters beyond speed - moving the cursor by hand is what a terminal is TOLD about, in an escape sequence, so redrawing on every keypress would fill every recorded transcript in this suite with them. The line is only reprinted when something happened in the middle of it. Where the line STARTS is worked out backwards from where printing ended, rather than trusted from what was remembered. That is what makes it survive the screen scrolling: a line printed on the bottom row moves everything up by one, and a remembered row would be one too low from then on. The command line holds 127 characters, up from 63. The limit started to be felt the moment a line could be moved about in. 58 recordings changed, and every one of them by the echo. THE PROOF IS NOT A HEURISTIC: a CosmOS built with the echo silenced reproduces 187 of the 188 recordings byte for byte. The one exception is cosmosTyped, the backspace test, where the rub-out marks now come from the shell instead of from the console's gatherer - same marks, different author. cosmosEditKeys is the new test, and every line in it is typed wrong and then corrected with a different key. Its last line is eighty six characters at a prompt in column two on an eighty column screen, so the line runs onto the row below and the shell has to find the start of something it can no longer see; breaking either half of that arithmetic fails it. Also: agree.sh looked for "> the same", anchored to a prompt that no longer precedes what a command prints. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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2a29cebc6b |
Make the screen come back on the machine people actually run
Found by running it: Grid exits and the shell prints its prompt into the grid, with the view up to seven pixels out of alignment. Three faults, and the first is the one that made the other two visible. MAKE RUN-VOYAGER HAD NO SCRATCH DRIVE. It gives drive 1 to Disks/personal.img, which is a file and not volatile, so there was nowhere to keep a screen - osTakeScreen answered no and the whole feature silently did not happen. It was tested with --ram-disk and shipped without one, which is as good a description of testing the wrong machine as I can write. There is now a RAM disk in drive 2, after the personal disk so that drive 1 stays the one that is yours. A PROGRAM TOLD NO MUST COPE. A refusal is not a fault, it means doing what the program did before there was anywhere to save a screen. Grid deleted its own tidying up when it started asking, so being refused left the grid on screen with a prompt written into it. It clears up again when refused, and only then. AND THE SYSTEM ALWAYS LEAVES THE SCREEN USABLE. The fine scroll registers go back to zero at every program exit, whether or not the picture could be saved: the console draws in whole cells, so a view three pixels into one puts every character three pixels out for ever. That is not part of saving a screen and should never have depended on it. Both paths are checked now. With a scratch drive the screen comes back cell for cell; without one, no grid is left behind. Breaking either fails one of them and not the other. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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ab72443b99 |
Give the screen back: osTakeScreen, and the RAM disk earns its keep
A program that takes the whole screen leaves the shell a blank one, and
whatever was on it is gone. There was nowhere to put 48K of video memory on
a machine with 64K of Data Memory that CosmOS already lives in.
A DRIVE MADE OF MEMORY IS SOMEWHERE. The screen goes to a file on the
scratch drive - the first volatile drive found at boot - like any other
file, and comes back from handleExit alongside the vectors and console mode
already put back there. The filesystem does the allocating, so this
invented nothing: it is 196 pages of tiles, map and palette, with a block
on the front holding the cursor, the four scroll registers and the mode.
NOT AUTOMATIC, and that is the whole design. Saving on every program start
would be cheap enough; restoring on every exit would be wrong, because dir
and Files and Say print and stop and their output is the reason you ran
them. A program says it took the screen, and one that says nothing behaves
exactly as every program did before this existed.
It deleted thirty lines of Grid, and they were all wrong anyway: four
scroll registers put back by hand, the map filled with spaces, the cursor
sent home, palette bank 0 written out - and the other fifteen banks kept
Grid's colours, because there was nowhere to have kept the real ones. Grid
is 64 bytes smaller and gives back what was actually there.
The check compares the screen before against the screen after, CELL BY
CELL, and allows only the rows around the cursor to differ - found from
where the text ends rather than guessed at, because the first version
assumed the cursor was near the bottom of the screen and let three real
differences through.
Two things cost time and neither was the feature:
- An edit adding "SWI osTakeScreen" to Grid was in the same script as a
failing s.index, so the file was never written - and the COMMENT
describing the call did land, from a later edit. Grid documented a call
it did not make, and read as though it should have worked.
- docs.sh caught osTakeScreen having no row in the services table, which
is the check the service layer added for exactly this and the second
time it has earned itself.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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AnachronautandClaude Opus 5
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04f1ffabd4 |
A disk made of memory, brought up by whoever owns it
THE MACHINE SUPPLIES BLOCKS AND SAYS WHAT A DRIVE IS. It says nothing about filesystems, which is what leaves room for a system that would rather have its own - and is why the volatile bit is a fact about the hardware rather than a promise about SBFS. 0x26 what the selected drive is: bit 0, contents do not survive 0x27, 0x28 how many blocks it has --ram-disk N a drive of N blocks with memory behind it A drive of memory selects, reads, writes and has a size like any other, and a program cannot tell the difference except by how fast it was. The one thing it cannot work out for itself is that the contents are volatile, because an empty disk and a volatile disk look identical from outside. THAT BIT IS THE DIFFERENCE BETWEEN A DRIVE A SYSTEM MAY FORMAT ON SIGHT AND ONE IT MUST NOT. CosmOS formats a volatile drive it cannot read, because there was never anything on it to lose, and leaves every other unreadable drive alone - an unformatted floppy is not an invitation, it is a blank floppy. Removing that check formats somebody's blank disk, which is checked rather than asserted: cosmosBlankDisk boots with one and requires it to be refused. So CosmOS grew a format. The size comes from the drive rather than from a superblock, since a superblock states a size too and that is no use on a disk which has not got one yet. Sixteen directory blocks, 128 names, chosen rather than worked out: a scratch disk runs out of names long before room, and this machine cannot divide. The RAM disk is no faster on this emulator by default, and that is honest rather than disappointing: the emulated disk has no seek time unless asked for one. With --disk-cycles 10000 the same copy is 7.94M cycles against 8.70M, the difference being every write. run.sh takes "ram:2048" where an image name goes, which needs no removing between runs because there is nothing to remove. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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3e48e9690d |
Put a disk of your own in drive 1
make run-voyager and make run-cosmos now attach Disks/personal.img as the second drive. It is made the first time it is wanted and then left alone: a rule with no prerequisites, so make never looks at it again. NOT UNDER build/, and that is the whole point. Everything else in this repository is made from source and can be thrown away without losing anything, so 'clean' empties build/ without a thought - and a disk of your own that a clean deletes is not a disk of your own. It is the one place here where something MADE ON THE MACHINE can live, which starts to matter the moment there are tools on it that make things. Disks/ is in .gitignore for the same reason: what you make on the machine is yours and not the repository's. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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e4f4bae762 |
Work across two disks: copy between them, and run a program from one on
files from the other Two things anybody expects of a second disk, and each needed something different. COPYING NEEDED TWO THINGS TO REMEMBER A DRIVE. The write stream is the only thing here that lives across service calls, so it is the only thing whose drive can change underneath it: every osFileBlock names its source path again and goes back to the source drive, and then osFileWrite has to come home. It records the drive it was opened on and returns there. And the file lookup CACHE. It keeps the last path resolved so a reader walking a file does not re-walk the directory for every block - and skipping the walk skipped the drive the path named, so block one of a cross-drive copy read the source's block numbers off the DESTINATION disk. It only showed on files of more than one block, because a file of one is never looked up twice. One block worked and two did not, which is a suspicious enough shape to have suspected sooner. RUNNING A PROGRAM FROM ELSEWHERE NEEDED A THIRD PLACE TO LOOK, and two restorations. The shell tried where you are and /Apps on the disk you are on. It now tries /Apps on drive 0 as well, which is what makes the system's programs work from a disk of your own - one with your files on it and no system, which is most of the point of having a second disk. The drive goes back after the load, because by then the program is in memory and the blocks it came from mean nothing; and again when it exits, because a program that copies between disks moves the drive as its own paths need to and being left wherever it finished is not what was asked for. Copy 1:/a 0:/b now leaves you exactly where you were. The fixture disk grew an /Apps, because it kept its programs at the root and so could not exercise the third place at all. Two hours of the debugging above were spent on a stale disk image. The machine boots the system that is ON the image, so a rebuilt cosmos.bin means nothing until the image is rebuilt too - and the trace said my new code never ran, which was true. Third time this project has been misled by one. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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4cc6393f5b |
Name a drive in a path
"1:/notes", or "1:" on its own for wherever that drive already was. Done in sbfsWalk, which is where every path in the system arrives - eight callers between the shell, the config reader and the filesystem - so it works for anything that takes a path rather than for whichever commands somebody remembered to change. NAMING A DRIVE GOES THERE AND STAYS THERE. Switching for the length of one command and switching back reads better and cannot work: a path resolves to a start block and a length, and those mean nothing without the drive they were read from. A load that resolved on drive 1 and then read its blocks on drive 0 would read the right blocks of the wrong disk. A name beginning with a digit is still a name. The colon is the whole of what tells them apart, and /2things is on the fixture disk to keep it that way. Two bugs, and the second is the interesting one. SUB sets carry on a BORROW, so a character below '0' leaves it set - and the test for "not a digit" branched on clear. Every prefix was ignored. Then the leading-separator test reads the first character through DP0, which sbfsPathDrive could not move because RET puts DP0 back the way it found it. It advanced SbfsPathAt and DP0 still pointed at the digit, so every prefixed path was judged relative and walked from the named drive's working directory. IT ONLY SHOWED WHEN THAT DRIVE WAS STANDING SOMEWHERE OTHER THAN ITS ROOT, because a relative walk from the root is an absolute one - so "cd 1:/2things" worked from a fresh boot and failed after "cd 1:/notes". The test does it in that order for that reason. Copying between two disks is still not one command: each path resolves on its own drive and the drive stays where the last path left it. That wants Copy to change drives between blocks. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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5644c24113 |
CosmOS knows about all four drives
A mounted disk is EIGHT BYTES - where its directory starts, how many
blocks it is, how big the disk is, and where you are on it. They now sit
together in the data segment, and changing drives is one copy out and one
copy in. The other three thousand lines of filesystem go on reading the
same four names they always have and never learn there is more than one
disk, which is the whole reason this was affordable.
The version is not in the record. It is checked at mount and thrown away,
because a version one disk's zero parent already reads as "in the root".
Every drive is mounted at boot: the controller says how many are plugged
in and each is tried in turn. One with nothing in it, or a disk this
cannot read, is left unmounted rather than stopping the others, so a
machine with a good disk in drive 0 and a blank in drive 1 starts.
'drive' says which one, 'drive 1' goes to another, and the working
directory goes with it - where you are on a disk is part of which disk you
are on. A drive the machine has not got is refused, and refused
differently from one that is there with nothing readable in it.
Three things the assembly caught me on, all the same misunderstanding of
what survives a call:
- OR reads A and B, and the bit came back from sbfsDriveBit in Q, which
RET does not disturb - but RET does put A back. The mounted mask never
got set and drive 0 was reported unmountable.
- MVQA then RSTA throws away the copy it just made, so doubling a bit
doubled nothing. SHL does it in one instruction, because A and B are
one register to it.
- There is no move from A to B. INB reads a port straight into B, which
is what the drive count comparison wanted.
run.sh takes more than one image now, separated by a plus, since the
machine has four drives and a test that could only name one could not
check any of this.
The buffer note is forgotten on a drive change and that is DELIBERATELY
kept although nothing can currently reach it: only the file read-ahead
consults it, a directory scan does not, and finding a file requires a
scan which overwrites the note on the way past. Two disks were built with
the same file at the same block to try to catch it and the answer was
right either way. Three instructions to hold an invariant rather than a
story about a bug - and the comment says so instead of claiming a fix.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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AnachronautandClaude Opus 5
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3b650cabcd |
Grid took the disk's bank number, and gave the screen back untidy
Found by playing with it: after running Grid, the shell could not start anything by name and dir said the disk was empty. Several commands after the program that did it had exited, and nothing had said a word. BANK NUMBERS ARE ONE NAMESPACE FOR THE WHOLE MACHINE. Grid registered video memory as bank 3, which is the number CosmOS gives the disk's buffer when it mounts - and that does not fail, it succeeds. Every read the filesystem made afterwards came out of video memory. Grid uses 4 now, and the CosmOS README has a table of who owns what, because the one place this was written down was a line in a service description about sbfsMount. Nothing hands bank numbers out and nothing refuses one that is taken. If programs start wanting banks routinely, a service that allocates them is what should exist rather than a longer table - noted there rather than built, since one program wanting one bank is not yet a system. Also puts the cursor home on the way out. The map was emptied and the console was not told, so the shell carried on writing from wherever the cursor had been standing when Grid started - twelve rows down a screen with nothing on it. Clearing is what homes a cursor and it costs one write. The regression test runs a program by name, then Grid, then the same program again; the second one is the check. Putting Grid back on bank 3 fails it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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1aa45fcfc4 |
Grid: fill the map, not the window
Scrolling sideways walked off the end of what the program had filled, so the grid went blank for six seconds and then came round again. A map row holds 128 cells - 256 bytes at two a cell, whatever mode the screen is in - and an eighty column screen shows eighty of them, so 48 were empty. This is the third thing this loop has counted and the first right one. It said forty, which filled half the screen. Then it asked the screen how wide it was, which fixed what could be seen and was still wrong. ASKING THE SCREEN IS RIGHT FOR FILLING A SCREEN AND WRONG FOR FILLING A MAP: a program writing one screenful wants the window, and a program that scrolls wants everything the window can be moved over. There is no register for that because it is a property of video memory rather than of the display. The check that should have caught it did not, and that is the more useful half. periodic.py looked at 32 pixels - four cells at the left edge - so it could not see a gap that was on the right, and at the cycle count it samples the origin had moved to column 22 and the gap was off in the middle distance. It reads the whole scanline now and says which column the picture stops repeating at, which is how the two failures above were told apart. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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bcd42e75ca |
Scroll the screen sideways, and by less than a cell
The screen could move one way, a cell at a time. Three registers were missing and this adds them: a column origin so the map can be wider than the screen as well as taller, and a pixel remainder for each axis so the step can be one pixel rather than eight. 0x36 Scroll column, in cells, wrapping at 128 0x37 Fine X, 0 to 7 pixels 0x38 Fine Y, 0 to 7 pixels FINE DOES NOT CARRY INTO COARSE. Writing 8 to a fine register writes 0, because only its low three bits mean anything. The alternative was for a write of 8 to step the coarse register, and it was rejected for one reason: a program that scrolls has to know where it has got to, and if the hardware carries then the only way to find out is to read the register back. Keeping them apart means the program already knows, because it did the arithmetic itself. It is also what the machines this one is pretending to be did. The renderer now draws one more row and one more column than fit and clips them, because with a fine offset the screen no longer begins on a cell boundary and the cells at two edges are partly off it. videoPutCell follows the column origin as it has always followed the row - a caller means a cell of the SCREEN, and the screen is a window onto the map. The fine offsets are deliberately not applied there: they move the finished picture by less than a cell, and there is no such thing as less than a cell to write into. So a program may scroll to any pixel without the console's idea of where row three, column five is moving underneath it. Grid now scrolls diagonally, a pixel a frame, in four port writes and two carries. It moved eight pixels every fourth frame before, which reads as the picture jumping rather than travelling. Seven checks, each one the same program with one register changed, so what is compared is where the picture stopped. Breaking fine X, fine Y, the column origin, the three-bit mask, or the console's use of the origin each fails exactly one of them. Grid's own two checks had to be rewritten, and the reason is worth keeping: they asked whether pixel 4 was a grid line, which was really a check that the scroll happened to be at a cell boundary. A picture that moves a pixel a frame can only be asked things that are true at every offset - that it repeats every eight pixels, and that one band of eight rows holds different colours from the next. Also repairs docs.sh, which found the minimal CosmOS application by taking the first asm block in the README. Documenting a program with an example above it made that a different block, and the check complained that the minimal application had no #Base about something that never claimed to be one. It looks under System Services now. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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1a8a5efe03 |
Grid: the first program to use the screen as a screen
Everything drawn on this machine so far has been text or a bitmap. The tile
engine has been there since the screen was built and only the console had
touched it, and only ever to put a letter in a cell - the one thing it can
do that a plain character display could do too.
Grid redefines a tile, fills all 128 map rows with it, and scrolls by
writing ONE BYTE A FRAME. Nothing moves. The rows above and below the
screen are already drawn, so a screenful of movement costs one OUTA and the
rows that leave the top are still there.
Its tile goes at 200 because the machine wakes with the font in tile memory
- glyph n at tile n, for 135 of the 256 - so a program starting at zero
paints over the alphabet and the shell it is about to hand the machine back
to. Its sixteen colour bands are one tile and not sixteen: the attribute
nibble is added to every index in a cell, so the same 64 bytes come out in
sixteen colourings.
Three things it cost, all of them the same lesson about this machine:
- "SETD.0 X" then "STD.0.1" stores through DP1, which had not been set
yet. It assembles, and the blit then reads its 64 bytes from wherever
DP1 was last left, so the tile came out as noise.
- The palette entry for scheme n is at 0xFC00 + 64n, which reaches
0xFFC0 - four pages, not one. And doubling A by adding B needs B to
hold A, which RSTB is the opposite of. Both went away by writing all
256 entries in order and letting the controller step the address, so
nothing computes an address at all.
- The screen it hands back had the right cells and the wrong colours,
because restoring the map is not restoring the palette.
That last one is a gap in the machine rather than in this program, and is
written up in the CosmOS README. The console's colours live at exactly the
entries the attribute nibble lands on, so any program using the nibble
overwrites them and has nowhere else to write. Grid puts bank 0 back - grey
on black - and leaves the other fifteen. The real answer is a command to
the screen meaning "give me back what you woke up with", the way the
console has one for clearing. There is not one, and this is the first
program that ever wanted it.
Two checks in video.sh, which boots the whole system and reads the pixels
the renderer produced rather than trusting what the program believed.
Breaking the tile fails one and breaking the attribute fails the other.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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AnachronautandClaude Opus 5
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553882d28d |
Start CosmOS with a script, and let a script hold its tongue
Three things scripts wanted, and they are one thing: a machine that can have a face. /System/Boot/startup.sh runs before anybody can type. Every way of reaching the prompt for the first time goes through it, including the one where there is no disk - in which case there is nothing to find and nothing is said. A MISSING one is ordinary and silent, because a clean install has none and a machine that complained every boot about a file nobody wrote would be teaching its owner to ignore it. One that is THERE and does not begin with #! is the other case entirely: somebody meant that to run. #quiet stops each line being echoed, #loud puts it back. The prompt and the echo go together, because together they are what makes a script look like typing, so a quiet script gets neither and what it prints is all that appears. A nested script inherits quiet - a build that asked for it meant its helpers too - and gets its own setting back when the helper returns. Anything else beginning with # is handed to the shell, which does not know it and stops the script, because a script that asked for something this shell cannot do should not carry on as though it had been given it. clear empties the screen, which the console has been able to do since before there was a screen to do it on. THE PROMPT IS NOW SAID BY WHOEVER SUPPLIES THE LINE. It used to be said at the top of the loop, which is a decision made before the line is read and an answer not known until after - and it was wrong at both ends. #quiet is itself a line, so its prompt went out before anything knew to stay silent; and the line after a quiet script's last one comes from the console, having already been denied one. Off by exactly one line in opposite directions. A first attempt at this remembered whether the prompt had been skipped, which worked and was a flag standing in for a structure. The monitor's assembler prints a prompt of its own, so it reads through shellReadRaw, which is the same source without one. One admission. Handing the console its prompt back when a quiet script ended was a real fix when I wrote it and stopped being one an hour later, because the restructure above means the console's own path prompts whatever the flag holds. The comment claimed it fixed something. Breaking it on purpose changed nothing, which is how that was found, and it is now a comment saying so instead of a line pretending to work. The startup fixture ends QUIET on purpose: nothing puts the flag back when the outermost script finishes, so a script ending #loud would have tested the easy half. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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c28826df77 |
Let a script run a script, four deep
A build script calling a setup script is the first thing anybody tries. What is saved when one script starts another is A POSITION AND NOT A BUFFER: the name, which block comes next, how many are left, and where in the block it had got to. Seventy bytes, and they sit next to each other in the data segment on purpose so that saving them is one copy. The block itself is read again on the way back, which costs one disk read per return and saves 257 bytes a level - the inner script reads its own block into the single buffer there is, so coming back means fetching the outer one's block again and landing on the byte it left. The slot is reached by stepping rather than by multiplying, because this machine has no multiply and the depth is never more than three steps. Four levels. Deep enough for a script calling a script that calls a helper, shallow enough that a script running itself says so rather than filling memory. A line that fails now stops every level and not just the innermost, because a build whose helper failed should not carry on in its caller. The caller's place is saved BEFORE the new file is looked at, and put back on every way out that is not success. Opening writes the name into the live state in order to ask the disk about it, so by the time "there is no such file" is known, the caller's place has already been overwritten - a failed 'do' inside a script would otherwise leave the script that ran it reading from a name it never chose. The test resumes in the outer script's SECOND block, which is the case the whole design turns on and the one an ordinary nesting test would miss. Breaking the re-read, the save, or the limit each fails it. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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a12d61fb80 |
Give the shell an echo, so a script can say what it is doing
Say.sbx has printed words since long before there were scripts, and is the wrong shape for one. It is a program: it has to be found on the disk, loaded and started, it prefixes what it was told with "it says:", and the system prints "finished" after it. Three lines of noise around one line of narration, and a load off the disk to produce them. echo is a command, so it costs a comparison. With nothing after it, a blank line - which is what anybody expects and is worth having to space a long script out. Not called "say", although that is the better word. Built-in commands are tried before the disk and always win, so a built-in say would shadow Say.sbx and quietly change what every existing script and test meant by it. Also puts "do" in the help, which the commit that added it forgot, and splits the help text: the new lines pushed it over the assembler's 255 character limit for one string. That failure was hidden for a few minutes by a 'make' whose errors were going to /dev/null - the build kept the disk it already had, and the machine cheerfully reported "I do not know: echo" from a system assembled before echo existed. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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2466d79d9c |
Let the shell run a file of commands
'do <file>' runs the lines in a file as though they had been typed. The
only thing a script changes is where the next line comes from: everything
below shellReadLine - splitting the line, matching it, loading a program -
cannot tell the difference and does not have to.
What makes a file a script is '#!' on the front of it, not its name and not
a flag in its entry. The rule this filesystem keeps is that an entry holds
only what the content cannot say about itself, and a script can say what it
is; the loader already refuses anything that is not SBEX, so the two kinds
of runnable file turn each other away without either knowing about the
other. It is also the deferred half of the file-typing design, which said
to wait for a second kind of runnable thing before building any of it. This
is that second kind.
'#' is a directive and ';' is a comment, as in SplitBit assembly - one rule
across the machine rather than two dialects. Not Unix's convention: there
'#!' really is a comment that only the kernel reads, while here the shell
requires it and refuses the file without it, so calling it a comment would
be a lie about what it does.
A script stops at the first line that does not work, which is what the
LineFailed groundwork was for. Comments and blank lines are dropped by the
reader rather than by the dispatch, so they are not echoed either. A script
running out hands back to the console rather than ending the shell, because
running out of file and running out of typing are not the same thing. The
interactive assembler reads through the same path, so a script can contain
a block of assembly.
Three things this cost that were not obvious:
- RET puts A and B back, so a routine cannot answer in them. scriptByte
returning the character in A assembled, ran, and handed the caller its
own A back every time. It answers in memory now.
- A last line with no newline is still a line. Text files do not reliably
end with one and an editor eating it is a bad way to find out a command
did not run.
- Not LastStatus. See the commit before this one.
Six checks in three tests, two of which are about byte positions rather
than behaviour - a command lying across the boundary between two blocks,
and that missing newline - so their fixtures are generated rather than
committed, where an editor cannot helpfully repair them.
Nesting is not in yet: a script cannot run a script. That wants a stack of
positions rather than the one the reader keeps.
Also derives native.sh's self-hosting source list from cosmos.asm's own
#Include lines. It was a hand written list and went stale the moment
script.asm existed - the fourth time a list beside a thing has drifted from
the thing - so it now asks the thing.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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AnachronautandClaude Opus 5
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e52d8d84f8 |
Collapse the two makefiles into one
Programs/makefile is gone and everything it did is here. The split was not paying for itself: nothing at this level ever ran that file, so it rotted, and all three bugs found in it this week share that one cause. It named two source files that had been renamed months earlier and failed outright. The disk did not depend on the tree it mirrors, so a new file silently was not on it. And the disk was in no default target, so 'make clean' threw it away and 'make' did not bring it back - which is what prompted this. The platform and the system stay separate, as TARGETS rather than as files: 'make SplitBit Assembler' builds the machine and its tools, 'make cosmos' and 'make disk' build the system, and somebody who wants to write their own system can ignore the second group entirely. That boundary is now one make enforces, which the directory boundary never did - Tests/makedisks.sh has always reached across it to build its own fixtures. 'make' now builds a bootable disk as well as the tools, because a machine with nothing in the drive does not do anything and the first thing anybody wants after building this is to watch CosmOS come up. It costs half a second: the whole system, twenty six apps and the native assembler assemble in less time than the emulator links. Two things the merge needed that the split did not. Assembling now takes an order-only dependency on the assembler, which came free when you had already built the tools before changing directory. And the mirror is told which directory to walk: it was ".", meaning Programs/, and left alone it would have meant the whole repository - the C sources, the tests and the manuals mirrored onto a disk for an 8-bit machine. The disk comes out at 188 files where it was 189. The one that went is Programs/makefile, which was itself being mirrored onto it as /Source/makefile. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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3da020898c |
Write down what the machine costs, before it has to be worked out again
Three measurements that would otherwise be re-derived from scratch in three months, put where a reader will meet them rather than where somebody has to know to look. The README's cost model section says what a nominal 1 MHz actually means: about 270,000 instructions a second, since the average instruction costs 3.72 cycles. The same program therefore takes 3.72 times the wall clock it did when a cycle was an instruction - nothing got slower, the number got honest, and the number it replaced described no machine anybody could build. Beside it, the two figures that put that in proportion: the emulator runs 195 million cycles a second in --fast, and CosmOS assembling CosmOS is 654 million of them, which is eleven minutes at a megahertz, 3.3 seconds at --fast, and six and a half seconds at a hypothetical 100 MHz. That last is pessimistic rather than hopeful: it assumes hardware overlaps nothing, which is the same conservative reading the controller's cost model takes. The CosmOS README gets what that means for its assembler, which is superlinear in what it reads: 1,383 cycles a byte for a four kilobyte source, 6,290 for a hundred kilobyte one. IT IS NOT THE DISK, and the number that says so is worth keeping - 654 million on a disk carrying the whole source tree against 653 million on a flat one with a sixth as many files. The suspected cause is walking a table of some nine hundred labels once per reference, suspected rather than measured. Nothing is being done about it, and the reason is written down too: development happens with the host assembler. But faster hardware buys a constant factor and does not change the shape of the curve, so the program that forces this is not CosmOS - it is the first one twice its size. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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7073b972e6 |
Say what went wrong, and give the file tools room for a path
The makefile on the disk was fine. "Makefile" is not "makefile", and SBFS names are case sensitive - but neither tool said so, and both failed in ways that pointed somewhere else. MORE PRINTED A NUMBER THAT MEANT NOTHING. "cannot find the file, error 2" invents a vocabulary the system does not have: the filesystem library documents its answer as zero or not zero, never as a code, so 2 could not be looked up anywhere. It says "there is no file by that name" now, which is the only way opening fails that a person can do anything about, and is nearly always a name typed slightly wrong. EDIT SAID "0 LINES", which is also what an empty file that IS on the disk says. A name typed slightly wrong therefore looked exactly like the document you meant to open, right up until you saved it somewhere new. It says "new file" instead. Two bugs came out of writing that, and both are worth more than the feature. The first is mine and the label lied to me: loadNothing is not where a load FAILS, it is where every load FINISHES, reached at the end of splitLast on files that opened perfectly well. A flag set there on the strength of the name was set on everything. It is called loadDone now, and the failure has its own name. The second is older and general: a program is loaded once and may be run many times, so "load Edit.sbx" then "run" twice is two sessions over one copy of the Data Segment. Anything a session changes has to be put back by the session. A zero written in the Data Segment is the state a program starts in the first time and never again - and cosmosEdit runs Edit twice from one load, which is why it caught it immediately. AND THE FILE TOOLS COULD NOT ADDRESS THE TREE THEY NOW HAVE. Edit took 23 characters of name and More and Type took 29, which were right when everything lived in the root. With the sources mirrored onto the disk, "/Source/CosmOS/Assembler/classify.asm" is an ordinary thing to type - thirty-seven characters, cut down to a name meaning something else, or nothing. All of them take sixty-three now, which is what the shell reads of a command line, so nothing longer can arrive. Wander with it, since a directory is a path too. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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0852666e73 |
Mirror the source tree onto the system disk
A list of files in a makefile goes stale the moment somebody adds a program and forgets to name it, and what they forgot is invisible until they go looking for it on the machine. So SplitDisk gained a mirror command and the disk rule is one line: putting a file where the others live is now the whole of putting it on the disk. EVERY FILE GOES THROUGH put AND EVERY DIRECTORY THROUGH mkdir. That is the point of it - mirror adds a walk and no filesystem code at all, so anything the format refuses here it refuses everywhere, in the same words. What is new is the walk, and the walk is what the six checks in Tests/disk.sh are about: that it goes all the way down, that it leaves dotfiles and named directories behind, and that a name too long stops it. REFUSED RATHER THAN SKIPPED, because a disk quietly missing a file is the exact failure a mirror exists to prevent. Which meant four sources had to be renamed - a directory entry holds 22 characters and they were 23, 23, 24 and 29: 16bitSegmentedSieve.asm -> 16bitSieve.asm 16bitSegmentedSieveModern.asm -> 16bitSieveModern.asm consoleInterruptTest.asm -> consoleInterrupt.asm controllerWriteTest.asm -> controllerWrite.asm The test names in the manifest are unchanged, since those are identifiers and every recorded result is filed under them. Only where the source lives has moved. The entries are sorted before anything is written. readdir hands them back in whatever order the host filesystem feels like, and a disk image that comes out different from one run to the next is an image no test could compare against another. The disk grew from one megabyte to four and from 192 directory entries to 1,024. The sources are 2,850 blocks and the mirror filled the old directory on its first run, which is a thing that should not need thinking about again. The Tests fixture disk is deliberately NOT mirrored. It is a controlled fixture with known contents, and the shipped disk is the one meant to be useful; they want different things. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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761c11a66b |
Add run-voyager, and make running depend on the disk
The jitter was a stale disk. An image built before the escape sequences came out still had the old Snake on it, which sends ESC [ H every frame: the console swallows the escape, because it is below the font's first character, and then draws "[H" as two ordinary letters. So every frame began two characters to the right and one line further down than the last, and the board walked down the screen. Not timing at all. WHAT IS ON A DISK IS WHATEVER WAS BUILT WHEN THE DISK WAS MADE, and a machine whose console has changed will start that image quite happily. That is the compatibility break we chose when the parser came out, and it is fine - but it should not be a puzzle, so both run targets depend on the disk rather than merely using it, and both READMEs say why. run-voyager boots the same disk on the machine with a screen. It existed only as EMU=../Voyager in front of run-cosmos, which is not a thing anybody should have to know. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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Anachronaut
|
79727044b7 |
Reboot, and the machine device that makes it possible
Until now the only way to restart was to stop the emulator and run it again, which meant the one thing the machine could not do was the thing Once was written for. The loop now closes without leaving it: > Once /System/Boot/bare.bin next start: /System/Boot/bare.bin, once > Reboot starting again stage two just this once: /System/Boot/bare.bin bare metal: no system, just this Writing 1 to port 0x13 asks the machine to start over. A PORT RATHER THAN A SERVICE, because a reset has to work when the system does not: something only askable through SWI would be unavailable in exactly the case that wants it most, and a program that owns the whole machine has no system to ask. It is device class 0x04, in the range kept for the machine rather than among the peripherals, because it is not one - it is not attached to anything and cannot be unplugged. WHAT A RESET REPEATS IS HOW THE MACHINE STARTED. Named an image, the emulator places it again; named none, the ROM is shadowed again and reads the disk. Anything else would mean a reset changed what the machine IS, which is the one thing a reset must not do. Both are tested. Taken between instructions, because a device cannot restart the machine from inside the instruction that asked: the CPU is part way through a step and its state is not yet anything a reset could leave behind consistently. The disk stays attached and keeps everything written to it - that is what warm means. The vector table is cleared, which is the one deliberate departure from leaving memory alone: a vector points into whatever installed it, and after a reset that program is not running, so a handler left behind would aim an interrupt at an address belonging to something gone. It is the argument CosmOS already makes at exit, applied to the machine. Reboot is 45 bytes, most of them the word it prints. |
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Anachronaut
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7b28f48f52 |
Once: start something else on the next start, and only that one
A program that owns the whole machine had nowhere to run. It cannot be started from the shell, because starting it means there is no shell, and pointing boot.cfg at it means a machine that keeps starting it - which is a poor place to find a mistake in something written five minutes ago. Once writes /System/Boot/once.cfg, in the same format as boot.cfg and read with the same routines, because a second format for one setting would be a second format. The loader reads it before boot.cfg and DELETES IT BEFORE IT JUMPS, which is the only moment there is: after the jump the loader does not exist. Consumed by being read rather than by working, so a one shot that hangs cannot hang twice - the request is gone before the image ran, and the next start reads boot.cfg like any other. THE BOOT STATE IS NOT TOUCHED, and the first version got that wrong. It marked the start the way any other start is marked, and then every successful bare metal boot reported that it had never arrived - because a program with the whole machine has no filesystem to clear a mark with and is doing nothing wrong by not having one. Found by running it: the image printed its line and the next start still said the last one did not. Three disks, each a start further along, so none of the tests depends on another having run. The loop is closed on the machine now: write it in Edit, assemble it with Asm, ask for it with Once, restart, watch it own the machine, and the system comes back without being asked. |
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Anachronaut
|
89c667848b |
Edit read a file into a buffer it never checked the size of
Opening hello.asm showed a thirty one line file as three, one of them cut short. Opening it again hung the machine: the emulator kept running and nothing ever answered. Entry is the buffer a line is read into, and it is followed in memory by TextHead and ArenaFree - the head of the document, and the pointer its line allocator hands out. The loop that splits a file into lines copied characters in WITH NO BOUND AT ALL, so a 94 character line wrote thirteen bytes over both of them. The list head then pointed into the middle of the text and the allocator handed out an address inside the file, which is why the second open walked a list that led back into itself for ever. Typing was always safe. osReadLine is told how much room there is, so a new document behaved perfectly and a source file did not - which is exactly how the user found it, and why it looked like a mystery rather than a bug. The bound is there now, and the buffer is 128 characters: what a line is everywhere else on this machine, the same number configuration files use, rather than a second answer to a question already answered. hello.asm fits. A file with a longer line is REFUSED rather than shortened. This is an editor - a line cut on the way in would be written back cut, and the file damaged by having been looked at. It says so and exits with a status of one, which it can do since this afternoon; the file is byte identical afterwards, and the test checks that. Opened twice in the test, because once is not enough to see it: the first open does the damage and the second is what never returns. This is the third time this shape has turned up: a buffer written past its end into the variables that happened to follow it. The prompt walked off CwdText into the shell's own command names; the assembler's output ran into its label table. Every one was found by a person using the machine. |
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Anachronaut
|
87d819847e |
A program can say how it went
SWI osExit takes a status in A, and the shell keeps it. Fifty eight exits across twenty three programs now say deliberately whether they worked: 25 did what they were asked, 24 did not, 9 were asked wrongly. Compare is the exception and says so - one there means the files differ, which is a result rather than a failure, the way diff has always had it. IN A RATHER THAN Q, which is not a departure from the rule that a service answers in Q. This one takes an ARGUMENT, the way osPrintNumber takes A and B, and it never returns to answer anything. A is free precisely because a return would have put it back - and Q is the ALU's output, so a small number costs four instructions there against one in A. The shell does not print it. A program that failed has already said so in words and a number beside that is noise, so osLastStatus hands it back and Status is the program that shows it. That indirection is the point: the number exists for the thing that cannot read words. MARKING THE EXITS FOUND A DEFECT ON THE FIRST RUN. Type and More printed why they had failed and then fell through into the success exit, reporting that all was well. Nobody had noticed, because while the only reader was a person, the person could see both the complaint and the claim. Two smaller things. Snake sets the console to line mode and then exits with zero, and the linter flagged the second RSTA as redundant - an exit status and a console mode, equal by accident, which is the class that must never be collapsed. And the README still taught answering by writing into the frame, three months of habit that SRET replaced yesterday; that section is gone and the one describing SRET stands in its place. |
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Anachronaut
|
b4206673a6 |
The clean install disk is one the machine can start itself from
make run-cosmos handed the emulator a boot image AND a disk, so it took the direct path every time: memory placed from outside, nothing on the disk consulted about it. The whole boot chain was built and tested and then not used by the one command that runs the system. The disk is formatted with a boot area now, stage two goes into slot zero as raw bytes, and the system is an ordinary file at /System/Boot/cosmos.bin - which is what boot.cfg would choose between if there were one. There is not: stage two falls back to that name when the file is missing, and a clean install with nothing to configure is the right default. run-cosmos names no image, so the machine starts itself. The old behaviour is run-cosmos-direct, which is worth keeping and worth naming honestly: it is what a debugger does, and it is what to use when the thing being debugged is the boot chain, since it skips the boot chain. /Source gains stage1.asm and stage2.asm, so the machine can rebuild what starts it. Everything stage two includes is already in /Lib, so Asm stage2.asm on the machine produces the bytes a boot slot takes. Stage one is the exception and always will be: it is the ROM, and the one part of this that a disk cannot replace. Second slot left empty, which is what makes replacing the first survivable. |
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Anachronaut
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c8c9f0b363 |
SRET: a handler answers the way a subroutine does
CALL saves A, B and Data Pointers 0 to 2 and nothing else, which is exactly why Q and DP3 are how a subroutine hands something back. An interrupt saves all of it, so a service with an answer had to reach into its own frame and un-save two fields by hand: MVSD.2 DPUP.2 0d02 ; the saved Q, by an offset it had to know STA.2 RETI Thirty places in CosmOS did that. Every one knew the frame's layout by heart, and all thirty would have gone quietly wrong the day the frame gained a field - the same duplicated fact this project keeps being bitten by, except duplicated into thirty places AND into the CPU. SRET is 0x76, in the seat the block split left for it. It is RETI's frame with RET's rule applied: A, B and DP0 to DP2 come back, the saved Q and DP3 are dropped, and the Interrupt Flag is restored from the frame - only that bit, so carry survives a service the way it survives a call, and there is one rule rather than two. RETI stays exactly as it was: a hardware handler has nothing to say and must leave no trace. CosmOS is 10,969 bytes against 11,122, and no handler knows a frame offset. TWO MISTAKES WORTH RECORDING, both mine, both caught by tests. The first conversion matched STA.2 with a regular expression that did not allow a trailing comment, so it ran past the end of one handler and into the next. The second understood the pattern and still got it wrong: the old frame write carried the answer from A into the saved Q slot, so simply deleting the write left Q holding whatever it happened to hold. Services that answer by calling something were fine - Q already had it - and services that set A directly silently reported success for every failure. cosmosCwd is what noticed, by saying "cannot go there" about a directory that was there. Sixteen handlers move the answer into Q now. Seven MVQA went with it. They copied Q into A so the frame write could carry it; SRET puts A back, so they moved a value nobody would ever read. |
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Anachronaut
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ce2a2cd7e6 |
Settle is a program, and a machine with no fallback still starts
The boot state opened a loop that could not be closed from inside: the machine said "settle it to try again" and gave you no way to do so. Settle closes it, in 349 bytes. A PROGRAM RATHER THAN A SHELL WORD. The shell is for the things that cannot be done without it, and this is not one - it reaches the system through SWI like anything else, which means it can be replaced, left off a disk, or called by whatever comes to call programs in turn. That last one is the point: a shell word is not callable by anything. Two services for it. osBootState answers in Q, and a machine with no disk answers settled, because there is nothing there to be unsettled about. osBootSettle puts it back. SETTLING IS THE ONLY WRITE A PROGRAM GETS - marking a start as trying or fallen back is the loader's business, and a service that let a program claim either would let it lie about something the loader has no way to check. And a hole the tests walked into, which was mine rather than theirs. With no fallback configured, a failed start left the machine unable to start at all: the mark said do not use the system, and there was nothing else to use. That turns "the last start failed" into "no start is permitted", which is worse than the problem the mark was added to solve. With nothing to fall back to it now tries the configuration again and says so - a failure that was passing recovers, and one that is not leaves the machine exactly where it would have been without any of this, which is the most that can be promised when there is only one thing to start. docs.sh caught both new services having no row in the services table before anything else did. |
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Anachronaut
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9c144469b4 |
Take the SplitLint findings that are one operation, leave the rest
Twenty four more sites, and the interesting part is which ones were left alone. A rule emerged while reading them and it held all the way through: apply where the repetition is INSIDE one operation, skip where the author's own structure says it is a new thought, and never where two equal values mean different things. Taken: - Five registers reassigned to a value they already held, where both are the same quantity: two masks in one expression in Snake, two spaces printed by the monitor, both halves of block zero in waitTest, and a RSTA in Pour that the very next instruction overwrote. - Eighteen SETDs that reload a pointer inside one operation - a store back into the variable just read, or an INCD stepping to the second byte of a two byte value. Those read correctly without the reload. - sbfsNext, which branched to the label on the line below it. Left, with reasons that are the useful part of this: - Eight registers where the same number means two different things. CosmOS and the loader set A to 1 for a blit command and then to 1 again for a bank number; Asm compares a type against 3 and then a status against 3. Removing those couples one quantity to another that is equal by accident and would part company silently. - Ten RSTAs that open the RSTA/RSTB/CCF/ADD "return zero" block. The redundancy is what makes that idiom self contained; taking it out makes the return value depend on the line above. - Eleven SETDs that begin an arm of a comparison chain. Each arm loads, compares and branches, and they get reordered - the repetition is the reason a new arm can be dropped in anywhere. - Twenty five SETDs separated from their pointer by a blank line or a comment, which is the author saying a new thought starts here. - Two CCFs before arithmetic, which this codebase writes unconditionally. - Three redundant branches in test programs whose recorded output includes addresses, where three fewer bytes moves what the test demonstrates. Nine recorded outputs moved and every one is a size in a listing or, for Life, five more generations inside the same cycle budget. Behaviour is unchanged everywhere: cosmosSnake and cosmosEdit pass byte for byte while Snake loses eight bytes and Edit twelve. CosmOS is 10,902 bytes of program against 10,937, and the native assembler 12,173 against 12,183. The CosmOS README's size for Edit moved twice in one sitting, and this morning's check caught it both times - which it could not have done before that claim was reworded to name what it was about. |
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Anachronaut
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e1273337c4 |
Two mechanical fixes SplitLint found: MVQA, and RSTA for zero
Twenty four places moved Q into A or B by pushing it and popping it back. That is four bus cycles and two bytes to do what MVQA does in one of each, and several of them are inside loops - Life, the calculator, int8. Nineteen more loaded zero with INIA 0d0 where RSTA says the same thing in one byte. Both are equivalent at the CPU rather than by assertion: RSTA and INIA both leave Status alone, and PSHQ followed by POPA nets to A = Q with the Stack Pointer where it started. The one difference is that the pair leaves a copy of Q in memory just below the Stack Pointer and MVQA does not, which nothing here reads. Five recorded outputs moved and every one of them says the change worked: - 16x16Life fits five more generations into the same cycle budget, the first 457 lines identical, because the loop got cheaper. - Life.sbx is 1409 bytes rather than 1411, in three tests that list it. - Edit.sbx is 1995 rather than 1996. That last one broke a check I added this morning, and the hole is worth recording: the CosmOS README's claim about Edit's size did not have the word "Edit" on the same line as the number, because the subject was in the sentence before, so the check that measures quoted sizes skipped it silently. The sentence now names what it is talking about, which makes it both checkable and clearer, and the check fails on a wrong number there. Comments on either half of a replaced pair are carried onto the instruction that replaces them, so nothing anybody wrote was lost. |
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Anachronaut
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8f4cc5878d |
Repair a table cut in half, and measure the numbers that had drifted
The README's emulator options table was split by forty lines of prose: two rows, then the whole discussion of the cost model, then five more rows with no header above them. Markdown renders that second half as something other than a table, so three of the seven options were not being shown as options. The rows are back together and the prose follows them. Four numbers had gone stale, in three different ways, and none was noticed: - "Five more scripts run alongside it" - there are six, and lint.sh had no bullet saying what it was for. - "rebuild all three tools" - there are four. - Files.asm quoted at 645 bytes in two places; it is 665. - Edit quoted at 1,983; it is 1,996. The last two are the most quotable sentences in the CosmOS README and the least likely to be rechecked by hand: the programs kept being made better and the sentences about how small they are stayed where they were. So docs.sh measures all four now. It counts the scripts in Tests/ that are not the driver or the disk builder and checks the README says that many and explains each one; it counts what the makefile's all target builds and checks the tool count in both phrasings, which took two attempts because one sentence says "the four tools" and the other "all four tools"; and it assembles every app the CosmOS README quotes a size for and compares. Each check was confirmed by making the fact wrong and watching it fail. WAIT also added a second kind of cycle this morning and the cost model section still described only one. It now says what an idle cycle is, why the two are counted apart, and what that distinction is FOR - a machine that slept through a slow disk and one that spun on it take the same elapsed time and print the same characters, and only the split tells them apart. The duplicated sentence about pipelining is gone; it was said twice, eleven lines apart, in nearly the same words. |
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Anachronaut
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c216c83e12 |
The filesystem waits for the disk instead of asking it repeatedly
sbfsWaitDisk spun on the status port. Read ahead had already hidden about
three quarters of the latency, and what remained was still 11.5% of Type
over a 14K file on a ten thousand cycle disk - all of it memory traffic
spent finding out that nothing had happened yet.
It tests the port first and only waits if the disk is still busy, and that
order is the whole of what makes it safe: the disk raises its line when it
finishes, so a disk that finished in the gap between the test and the WAIT
has its line standing already and the WAIT does nothing rather than
sleeping through the answer. No handler and no vector - the shell keeps the
Interrupt Flag down, and a WAIT wakes on a line whether or not anybody
means to answer it.
Printing a 14K file, by where the cycles go:
cycles a block total bus waiting
0 922,570 922,570 0
2,000 946,474 922,702 23,772
10,000 1,042,474 922,702 119,772
The bus column stops moving. What the program costs in memory is now the
same whatever the disk does. On this emulator nothing observable changes;
on hardware it is a CPU standing out of the way of the memory controller
rather than competing with it for every one of those 119,772 cycles.
The first version cost 660 cycles more at latency zero because it read the
status port again on the way out. AND writes to Q and leaves A alone, so
the status was already there - which is what the original said in its own
comment, and what I stopped believing while rewriting around it.
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Anachronaut
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ce0f18f4ef |
Refuse a directory whose last entries cannot be named as a parent
A parent is an entry index PLUS ONE in two bytes, so entry 65535 has no parent number: adding one wraps to zero, and zero is the root. Eight entries to a block, so 8192 directory blocks reaches it and SplitDisk formatted that happily. It does not fail by refusing, which is why it was worth chasing rather than reasoning about. Reproduced on a disk built for it: mkdir /deep/child, with /deep at entry 65535, printed 'Made "/deep/child" as entry 0' and put child in the ROOT. Listing /deep then showed nothing, because the search is for a parent of 65536 and the entry carries zero - so the same mkdir succeeded again, and again, and five entries called /child piled up in the root. Duplicate names in one directory are the one thing rename refuses outright, on the grounds that a search answers with whichever it meets first and the rest can never be reached; this manufactured them one per attempt. 8191 blocks is the most, giving 65528 entries. Refused when formatting and again when reading, in both implementations, because a disk claiming more was made by something that never checked. On the machine only the high byte of the count has to be looked at: anything from 0x20 up is too many. Three checks, all of which fail with their guard removed. The machine's disk claims the size rather than having it, so the test image is 64 blocks that lie rather than sixteen megabytes that do not - mounting is refused at the geometry, which is read out of block 0. |
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Anachronaut
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2b5506ee70 |
Stop the prompt writing off the front of its own buffer
The prompt is the working directory's path, worked out each time by walking the chain of parents up to the root. The names arrive deepest first, so they are written backwards from the end of a 127 byte buffer - and nothing bounded that walk. Nothing bounds the depth either. A path given to one operation is capped at 95 characters and a 22 character name, but "mkdir a" and "cd a" are each far inside that and can be repeated forever. Six directories of 22 characters is 132 characters of path, and at that point the walk wrote down past the front of CwdText and into what the assembler had laid out below it: the shell's own command names. ExitName sits five bytes under, so the word "exit" went first and the shell stopped recognising the command for leaving. Measured, not deduced: fine at five levels, gone at six. The walk now counts the room it has left, byte by byte, and stops. What is already written is the DEEP end of the path, which is the end worth showing, so it is cut at the front and three dots say so - out of three bytes held back from the count, so there is always somewhere to put them. Twenty levels deep the prompt shows the last five and every command still works. cosmosDeep records that, and records it by running help, cd and exit from down there rather than by looking at the prompt: a wrong prompt is cosmetic, and this was writing into other variables. It fails with the bound removed. The tree is built by SplitDisk because a path that long cannot be given to mkdir in one piece - which is the same fact that makes the depth unbounded. The three path limits are written down in the README now, including which one actually binds. The other two do not: the longest path on a full install is 21 characters. |
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Anachronaut
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ce8fb721fe |
Say a temporary is one in the entry, not in its name
Saving something that already exists writes a temporary, deletes the original and gives the temporary its name, so that nothing is lost if the writing fails. The temporary was told apart from a real file by being called sbfs.part or sbfs.out - and those are legal names. Starting a save deleted whatever answered to one as stale scratch, so saving anything at all in a directory destroyed your own file of that name there, silently. Flag bit 0x04 now says it. The property is not in the contents - the same bytes become the finished file the instant the rename lands - so it belongs in the entry, which is the thing the commit changes. sbfsCreateTempAt is the door temporaries come in by, the commit writes the flags flat along with the name, and cleanup wipes what it finds only if the entry says it is ours. Anything else stops the save instead. The bit is also the recovery. Both listings show an unfinished write rather than sizing it, because the size in the entry is the room that was asked for and not what was written: "<unfinished>" from dir, and a line from SplitDisk saying the blocks are held and a rename brings the data back. That was the gap in what the last commit documented - the data survived a crash and nothing would show you where it was. Four new agreement checks, three of which fail with the guards removed. The fourth needed rebuilding first: both tests started on one disk, and the first save ate the sbfs.part that was the second test's SOURCE, so the copy failed for want of a file, never opened a stream, and passed while reporting on nothing. A disk each. The fifth check forges the wreckage by setting the flag on a finished file, since nothing here can crash a save half way through. No version bump: a committed file never carries the bit, so a disk this writes is byte for byte the disk the old code wrote, which the whole-image comparisons confirm. Only the wreckage differs, and older code reads that as an ordinary file - which is what it did before. |
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Anachronaut
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9e2aa0122e |
Say what a safe save actually promises, and where it stops
Both sbfsSaveFile and sbfsStreamDone write a temporary, delete the original and rename the temporary onto its name, and the README explained why that order and not the obvious one. It never said what the resulting guarantee is, which invited the stronger reading: "safe save" sounds like it survives anything. It survives everything that goes wrong while it is running - no run long enough, no free blocks, a refused write, a name that turns out to be a directory, a writer that gives up - and in all of those the original is untouched. It does not survive the machine stopping, because the commit is two block writes with a gap between them: stop there and the old file is gone and the new one is still called sbfs.part. The bytes are all present and one rename by hand recovers them, but nothing does that on its own. Written down in the README beside the ordering it qualifies, and at both commit points in sbfs.asm, where a reader is when the question occurs to them. Closing the gap wants a journal or a second directory, which is a lot of disk for two writes; a boot-time consistency check is the cheaper answer if it ever matters, and it would want temporaries flagged in the entry rather than recognised by name. |
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Anachronaut
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aa7bdc6acd |
Check the memory map against itself, not only against the code
The CosmOS README's Data row gave the system 0x0000-0x3FFF and a loaded application 0x2000 and above: two columns of one row that cannot both be true. Program was doubled to 0x3FFF when CosmOS outgrew its first map and that number was copied into the Data row as well, where the answer is 0x1FFF. docs.sh measured both segments against the CosmOS column and passed the table anyway, because it never read the column beside it. A number checked against the code and not against the number next to it is still unchecked, so it now reads both and compares them - and compares two further copies of the same fact that had gone stale on their own: the minimal application in the README, still based where applications lived before the doubling, and the map cosmos.asm opens with, which somebody reading the system reads before they read the README. Each of the three checks was confirmed by breaking the fact and watching it fail; the first reproduces exactly the text this commit removes. While in that header, the command list said five commands and CosmOS has eleven and a search path besides, and "dump is next" outlived the monitor. |
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AnachronautandClaude Opus 5
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db3d349da8 |
Read the next block while the program is busy with this one
A file is read front to back, so when something asks for a block, the one after it is almost certainly wanted next. sbfsReadOne asks the disk for it straight away and hands back the block that was wanted - so the transfer happens while the caller is busy, and the waiting is mostly over by the time it comes back. Printing a fourteen kilobyte file: 1,064,498 cycles at two thousand a block becomes 976,882, and 1,576,562 at ten thousand becomes 1,032,889. The second figure barely moves between those - seven per cent from an instant disk to a slow one, where without it the same change costs sixty eight. A machine that reads ahead stops caring very much how fast its disk is. NOT FOR DIRECTORY SEARCHES, and that was tried first and thrown away. A scan stops the moment it matches, so the block it would read ahead is one nobody will ever look at - a transfer to fetch and another wait to throw away. It was nineteen per cent SLOWER on a lookup at ten thousand cycles a block. Reading ahead is a bet that the next block is wanted, and a search is exactly the case that hopes it is not. The scan loop is untouched. Three per cent is what it costs when the disk is instant, which is the bookkeeping with nothing to hide behind it, and the default. The disk has one buffer, so the only way to know what is in it is to remember what was last asked for. Every read records that; a write clears it, because a write fills the buffer from memory and no read asked for what is in it. Getting that wrong would blit whatever happened to be there and call it the block somebody wanted. The read ahead is bounded by the file's own length, so reading the last block does not fetch whatever follows the file on the disk - which belongs to somebody else and would be paid for twice, once to fetch and once to discard. It cost one bug, and an instructive one: the next index was worked out by stepping SbfsIndex, which is the CALLER'S and is still wanted after the return - handleFileBlock compares it against the file's length to see whether this was the short last block. Every block reported the wrong number of bytes, and the output of Type skipped five lines in the middle. It has a place of its own now. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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54f5cfe8a4 |
Add Copy and Compare, which stream in both directions at once
Copy joins the read and write streaming services: source and destination are both larger than Data Memory while the program owns one block. Compare reads two files through separate blocks and ignores the bytes past a short final block, which belong to neither file. Between them they exercise empty, exact-block, part-block and 84,000 byte files, and the host extracts the copy afterwards so that two native programs agreeing with each other is not the only oracle. Written by ChatGPT, as their headers record, along with the agree.sh section and the manifest entry that drive them. THIS SHOULD HAVE COME FIRST. The commit before it staged whole files rather than the hunks it meant, so its manifest already names these two programs while their source was still untracked - that commit will not build on its own. Left in place rather than rewritten, since the pair is right and only their order is wrong. NOTES.md is their review of the streaming work. The first item in it is fixed by the commit before this one; the rest are still open. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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fb7b224bbb |
S2: the assembler writes the file as it makes it
The output image is gone. It was eighteen kilobytes and it is now one block of window, because the file was always produced in order and only ever needed to be written that way. Everything works in FILE OFFSETS now. A cursor is a two byte number counting from the front of the file, and since a block is two hundred and fifty six bytes, the block it lands in is the offset's high byte and the place within that block is its low one - so there is no division anywhere, and ImgWalk, ProgPut and DataPut needed no change but where they start. ONE WINDOW RATHER THAN THREE. The plan said three: one per segment, and a third for the block where the program ends and the data begins, which belongs to both. Fetching a block back instead makes all of that one case. The header is patched after every byte is out, the boundary block is written by both cursors, and both are simply revisits - a revisit is what fetching handles. osFileFetch is the service that allows it, and is the read side of the write. A run of bytes in one segment costs nothing extra; a switch between segments costs two block operations, and a source file has a few dozen switches and several thousand bytes. Two bugs, both a pointer meaning two things: putAt took the cursor to advance in DP2 and then wanted DP2 for the window's address. A call puts DP2 back the way it was AT THE CALL, so the step at the end moved whatever the last call had left there - the window walked off across memory while the cursor stood still. It goes in memory now, like the block did in S1, and for the same reason. The size the file is created at could not be right. How many vectors are actually installed is not known until the second pass has resolved their handlers, and by then the file must already exist to be written into - so Keys, which brings one vector, came out four bytes short. Teaching the first pass to count them meant teaching it about devices, and about a Boot line in a loadable program not being installed at all, which is two ways to disagree with the second pass about what a file contains. So osFileDone is told the size instead. A writer asks for as much as the file could possibly come to - the whole of it plus four bytes for every vector DECLARED, which no file can exceed - and says what it really came to at the end. The blocks it did not use go back to the free count. Asking for too much costs a moment; asking for too little writes off the end of a file. That is a better service for it, not a workaround. A writer that cannot know its size until the last byte is the ordinary case, and it is exactly the case this whole rung exists for. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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9f7dffdeca |
S1: the write side learns to stream
osFileStart, osFileWrite and osFileDone are the mirror of osFileInfo and osFileBlock. A program can now write a file it never holds: Pour writes twelve blocks and a tail while keeping 256 bytes of it at a time, and the host tool reads all 3,112 bytes back with every block where it was put. ONE WRITE IS OPEN AT A TIME AND COSMOS HOLDS IT. Reading needs no state - a name and an index are the whole question - but writing safely does, because the new file has to exist before the old one is thrown away and something has to remember which temporary belongs to which name. Keeping that here means the careful order is written once instead of in every program that streams. Nothing already on the disk is touched until osFileDone, so a disk without room says so while the old file is still there. That is stronger than osFileSave can manage, where the size is only known once the caller has every byte in hand. osFileSave stays: Edit and Files hand over whole documents and have no reason to learn any of this. osFileWrite refuses an index past the end of the file, and that refusal is not politeness. Files are contiguous, so block nine of a three block file is a real block belonging to something else, and writing it would put one file's bytes inside another with nothing anywhere saying so. Checked both ways: the tail block is allowed and the one past it is not. Three bugs, all of them the same shape - a register or pointer used for two things at once: DP3 carried the block count in and was popped high byte first, which is the wrong way round from every reader in the system and made the count two hundred and fifty six times too big. sbfsStreamStart took the name in DP0 and then wanted DP0 for something else before it had read it, so it walked whatever it last pointed at and reported that it could find no room. sbfsStreamWrite kept the caller's block in DP3 across a find - DP3 being the pointer a return does not put back, which is exactly why the find uses it too. What went to the disk was whatever the scan last looked at. It goes in memory now, and the file is correct because every block says which block it is; a check on the length alone would have passed all three of these. Writing no longer finds the file for each block either. Nothing moves a file once it is made, so where it starts is settled when the temporary is created. That was not even slow - a scan stops the moment it matches - but it was a walk of the directory per block for an answer that cannot change, and it is 28 per cent of the cost of writing forty blocks. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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06bdbf7728 |
D5: move in, and give the assembler somewhere to look
The demo disk is three directories instead of thirty nine names in one list with cosmos.asm sitting between fileStream.asm and sbfs.asm: /Apps what you run /Source what you name to the assembler /Lib what those include The split is by ROLE rather than by which directory the host keeps a file in. Everything in /Lib is named by an #Include somewhere and by nothing else, which is what makes it a library rather than a source. THAT LAYOUT WAS NOT POSSIBLE UNTIL NOW, and finding out why is what this rung actually cost. An include on the machine was a bare name resolved where you stood, so every source that calls a service had to sit in the same directory as services.asm - which is every source worth having. The first arrangement of this disk put the examples in a directory of their own and none of them would assemble. So the native assembler has a search path: beside you, then /Lib. The same rule the shell already uses for a program it does not recognise, applied to the thing that reads source, and the same reasoning for it being two fixed places rather than a list - a list needs somewhere to live between one boot and the next, and there is no such place yet. It also brings the native assembler nearer the host one, which has searched -I directories since before there was a machine to run this on. The reader's per-file state grew from 293 bytes to 301, because the name it keeps is a path now and every block of a file is asked for by it. Six of those would no longer fit the room set aside, so the include list moved up a page. Both numbers are written down in two places on purpose and both were changed. dir said cosmos.asm was 17,460 bytes. It is 82,996. The size came out of the block count's LOW BYTE shifted up and the tail beneath it, which is sixteen bits, so anything from 256 blocks upward came back as itself less 65,536 - a plausible number, and wrong. Files that big say their size in blocks now. Printing the true figure wants decimal printing twenty four bits wide, which is a page of console.asm to say something nobody reads more precisely than "big". The Assembler Manual's line about SBFS being flat was the last thing in the repository still claiming it, and docs.sh now looks for that phrase and three like it in all four documents. Not a section that is wrong - one clause inside a paragraph that is otherwise right, which is the shape this kind of staleness takes. The duplicate puts are gone with the wildcard that caused them, so building the disk is quiet. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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da91a36d92 |
D4: the machine makes directories too
mkdir and rmdir are the machine's own now, and a file goes where its path says rather than always in the root. A disk can be organised without the host tool touching it. Everything below the surface works in terms of a directory and a name rather than a path. sbfsWalkParent splits the last name off, walks the rest, and hands back the two - and the separator stays on the end of the head, which is what makes one rule cover every kind of path: "/x" leaves "/", which is the root; "x" leaves nothing, which is where the machine already is; and "A/x" leaves "A/", which is neither and needs no special case to say so. Saving works in those two as well, and had to. The careful order a save uses - make a temporary, write it, delete the original, rename the temporary - only works if the temporary is made in the SAME directory as the file, because the rename at the end changes a name and does not move anything. Renaming to a path naming a different directory is refused for that reason, rather than quietly being a lie the disk goes along with. Three things this cost, all found by running it: mkdir Apps/Deep made /Apps/Apps. The leaf was worked out into SbfsWanted and then the head was walked - and walking goes through sbfsPathNext, which puts every name it meets into SbfsWanted on the way past. The head's last name landed exactly where the leaf was. It has somewhere of its own now. rmdir took a directory with something still in it, which is the one failure the whole design is arranged to prevent. Looking for children clobbered DP2 and rebuilt it from the buffer and the entry count with the subtraction the wrong way round, so the pointer walked off the end of the block and found nothing. The comparison goes through a CALL now, like the two beside it, and DP2 comes back on the entry because a RET puts it there. SplitDisk's "in use but not reachable from the root" line is what caught it. Refusing a name longer than twenty two used to read the twenty third character of a shorter one, which is somebody else's string. It is measured now. Tests/agree.sh is new and is the gate this rung was for: the same disk built twice, once with SplitDisk and once with CosmOS, compared byte for byte. The two share no code and only a written specification, and every field one writes and the other only reads is checked there and nowhere else - which entry a thing lands in, which block, what a directory's unused fields hold, the version, the free count. It caught a wrong parent immediately when that was broken on purpose. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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36ce9f6ccf |
D3: the machine knows where it is
cd moves it, dir lists the directory it is in, and the prompt says which one - but only when that is not the root, so a machine nobody has moved about on looks exactly as it always did and every recorded test that never says "cd" keeps its recorded prompt. A path beginning with a separator is measured from the root and anything else from where the machine is, so a bare name means a file in the current directory. NO PROGRAM HAD TO BE TOLD: the working directory lives in sbfs.asm beside the thing that resolves paths, because it is what a relative path MEANS. Keeping it in the shell would have meant either handing it down on every call or pasting it onto the front of every name, and the second of those is how a name that is already absolute gets ruined. Nothing stores the path. The working directory is an entry index and two bytes, and the text on the prompt is built each time by walking the chain of parents upward, writing names from the end of a buffer towards the front - which is the order they arrive in, and saves reversing them afterwards. sbfsFind splits into a walk and a check. "cd /" and "cd .." both end at the root quite legitimately, and had no way to say so through a routine whose only word for the root was "missing". Typing a program's name now tries two places in order: where you are, then /Apps. The first makes a program you are working on the one that runs; the second lets Snake work from anywhere. A word already beginning with a separator has said where to look, so only that place is tried. osChangeDir exists so that "a program may move about, and the shell puts the working directory back" is a thing that can happen rather than a promise about nothing. Both halves of that were unfalsifiable without it: with no way for a program to move, removing the restore changed no test. Wander is the program that moves - it goes where it is told and reads a file there by a bare name - and with it on the disk, removing the restore fails. The remembered file is dropped whenever what a relative path means changes: a cd, a program calling osChangeDir, a program exiting. Removing all of them fails the test and removing any one of them does not, because today every path into that cache belongs to a program that exits. It is kept in all three because the cost is a call and the failure is a file's blocks being handed out under another file's name. The cwd fixture holds two files called notes.txt saying different things, and a Say.sbx in /A that is really hello. Two copies of one program, or two copies of one file, would have passed with the whole of this deleted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |
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AnachronautandClaude Opus 5
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588e02aff5 |
Double CosmOS's half of the machine, and check that it fits
The memory map gave CosmOS 0x0000 through 0x1FFF of Program Memory and applications 0x2000 and above. CosmOS is 8141 bytes at the previous commit, which is fifty one bytes short of the line, and the next thing added to it went over. GOING OVER DOES NOT FAIL WHERE IT HAPPENS. Nothing enforces the division: an application says where it goes with #Base and the loader puts it there, so a CosmOS that has grown past 0x1FFF simply has the next program loaded written over the end of it. What breaks is whichever part of the shell that program happened to cover, at whatever later moment somebody uses it. It turned up here as the monitor's assemble command answering "I do not know" to valid instructions, several commands into a session, on a machine that had booted perfectly well. Both halves are doubled: applications now start at 0x4000 in Program Memory and 0x2000 in Data Memory. That is 16K of code and 8K of data for the system, against the 8775 and 2948 it uses today. Both were on the same trajectory, and moving them together means the twenty files that say #Base are edited once rather than twice. The standalone loader's loadable.asm keeps its old base: it belongs to the loader CosmOS grew out of, not to CosmOS, and its addresses answer to a different program. The unbased-segment diagnostic keeps its old base too - it exists to produce an error message that names the address, and the message is what is recorded. Tests/docs.sh now reads the two limits out of the table in the README and measures both segments against them. It reads them rather than being told them because the table is the specification, and this is the second time in this project that the thing nobody checked is the thing that rotted. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com> Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW |