The shell printed "finished" every time a program gave the machine back.
That made sense when starting a program and getting the machine back was
most of what the machine did and the prompt was the only other thing on
the screen. Under a listing, between two commands, it is noise.
And it was printed whatever the program made of it, so a program that had
just explained what went wrong was answered with the word "finished" -
"there is no such directory: nowhere" and then, immediately, "finished".
The prompt coming back is what says a program is over. It is the same
argument osLastStatus is made of: a program that failed has already said
so in words, and anything the shell adds beside that is the shell talking
over it. A program that FAULTED still says so, because the fault screen
printed in red above and a program that is gone should not look like one
that ended.
A NEWLINE ONLY IF ONE IS WANTED. A program that stopped part way along a
line would leave the prompt sitting in the middle of its last output,
which the word used to prevent by accident. The console knows which
column the cursor is in, so the shell asks - where a blank line printed
every time would be right about half of the time, and an empty directory
listed with ls would be followed by a blank line for no reason.
Fifty nine recorded sessions lose the word. Two of them move a cursor up
a row with it, which is the same fact seen from the screen.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
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
AnachronautandClaude Opus 5