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Put a reset button on the case, and stop Escape closing the window

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ESCAPE WAS A BUG I LEFT. This machine sends Escape to the console like any other key, and
Raylib closes a window on Escape unless it is told not to - so a program reading keys could
be ended by one of them, taking whatever was in memory with it. SetExitKey(KEY_NULL), and it
is a byte again.

F12 is the reset button. A button on the case rather than a key the machine can see: nothing
sends a function key to the console, so nothing can be surprised by one. It does what writing
MACHINE_RESET does, which is that the machine starts the way it started - the boot chain runs
again and finds whatever the disk now says to run.

Which is what makes a bare metal program escapable. Once puts a demo in front of the next
start and deletes the request before jumping, so a demo that has taken the whole machine is
one keypress from the system coming back, instead of closing the window and opening it again.

IT HAD TO REACH A MACHINE THAT IS WAITING, and that took two more things. A reset is acted on
between instructions, and a machine blocked on a key is part way through one - so the button
would have set a flag that nothing ever came along to notice, in exactly the situation a
reset button is for. The wait ends now: the console is told its input is over, which it is
for a machine about to stop existing.

And the reset puts the console's input back - nothing pushed back, no line half gathered, and
not at the end of input. That was already wrong before the button existed: a reset after the
input ran out left a console that had run out afterwards, so a machine could be restarted
once and then never typed at again.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01E2JrLzFvuFX9fgi1LDRjrW
This commit is contained in:
Anachronaut
2026-08-29 11:05:16 -04:00
co-authored by Claude Opus 5
parent 13b20c8834
commit f7657081be
5 changed files with 86 additions and 0 deletions
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Source/Emulator/io.h
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@@ -306,6 +306,19 @@ void serviceDevices(void);
// the instruction that asked - the CPU is mid-step and its state is not yet consistent.
int takeResetRequest(void);
// ---- The button on the front of the case ----
//
// A machine has one, and a window is the case. Writing MACHINE_RESET is how a PROGRAM asks;
// this is how a person does, without needing a program that is willing to listen - which is
// the whole point of a reset button and the reason the port exists at all.
void requestReset(void);
// Puts the console's input back to how a machine starts: nothing pushed back, no line half
// gathered, and NOT at the end of input. Called when the machine starts over, because a
// console that had run out of input would still have run out afterwards - and a reset that
// left the keyboard dead would be a reset nobody could use twice.
void consoleResetInput(void);
void raiseInterrupt(uint8_t port);
void clearInterrupt(uint8_t port);