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Grid took the disk's bank number, and gave the screen back untidy

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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
This commit is contained in:
Anachronaut
2026-08-30 21:14:07 -04:00
co-authored by Claude Opus 5
parent 1aa45fcfc4
commit 3b650cabcd
8 changed files with 94 additions and 9 deletions
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Programs/CosmOS/README.md
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@@ -797,6 +797,31 @@ An application may also include its own libraries or access hardware ports direc
The services are an interface offered by the system, not the only way software is allowed
to use the computer.
### Bank Numbers Are One Namespace:
A program that wants a device's memory registers it as a bank, and **bank numbers belong to
the whole machine**. Nothing hands them out and nothing refuses a number that is already
spoken for - registering one that is taken does not fail, it succeeds, and whatever held it
before quietly answers to nothing.
| Bank | Whose |
| --- | --- |
| 0 | Program Memory. The machine's. |
| 1 | Data Memory. The machine's. |
| 2 | The bank table. The machine's. |
| 3 | The disk's buffer, given at mount by `sbfsMount`. CosmOS needs it for as long as it is running. |
| 4 and up | Free for a program to use. |
`Grid` learned this the hard way and is the reason the table is here. It asked for 3, took the
disk's buffer, and every read the filesystem made afterwards came out of video memory - so the
shell found an empty disk and could not start anything by name, several commands after the
program that did it had exited. Nothing said a word, because from the controller's point of
view nothing went wrong.
**A program returns a bank by giving it back**, which today means knowing what was there
before. There is no service that hands out a free number, and if this becomes a common thing
for programs to want then that is what should exist rather than a longer table.
## What A Program May Ask The System For:
A loaded program is on its own hardware and can do anything the machine can do - it is a fence, not a wall. But the things it usually wants are things the system is already doing, and asking is both shorter and the only way to reach code that was assembled separately. `CALL` needs a label, and a label has to be in the same assembly; `SWI` needs only a number both sides agree on.