Difference between revisions of "Input"
From SizeCoding
(Created page with "== Checking for ESCAPE == This is fairly easy: Monitor the keyboard scancode port for ESC which is #1, then deal with it: <syntaxhighlight lang=nasm> in al,60h...") |
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jnz mainloop ;fall through if 0, do jump somewhere else if otherwise | jnz mainloop ;fall through if 0, do jump somewhere else if otherwise | ||
</syntaxhighlight> | </syntaxhighlight> | ||
| + | |||
| + | == Checking for '''any''' keypress == | ||
| + | |||
| + | If you need to shave a byte, it might be possible in some environments to check for any keypress instead of just escape using less code: | ||
| + | |||
| + | <syntaxhighlight lang=nasm> | ||
| + | in al,60h ;read whatever is at keyboard port | ||
| + | das ;If non-zero, parity will be set | ||
| + | jp mainloop ;Jump if parity | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | An alternative if not running DOSBox: | ||
| + | |||
| + | <syntaxhighlight lang=nasm> | ||
| + | in al,60h ;read whatever is at keyboard port | ||
| + | aaa | ||
| + | jz mainloop ;Jump if zero | ||
| + | </syntaxhighlight> | ||
| + | |||
| + | The above are somewhat flaky due to different hardware, VMs, and emulators not honoring flags correctly. | ||
Revision as of 00:57, 7 August 2016
Checking for ESCAPE
This is fairly easy: Monitor the keyboard scancode port for ESC which is #1, then deal with it:
in al,60h ;read whatever is at keyboard port; looking for ESC which is #1
dec ax ;if ESC, AX now 0
jnz mainloop ;fall through if 0, do jump somewhere else if otherwise
Checking for any keypress
If you need to shave a byte, it might be possible in some environments to check for any keypress instead of just escape using less code:
in al,60h ;read whatever is at keyboard port
das ;If non-zero, parity will be set
jp mainloop ;Jump if parity
An alternative if not running DOSBox:
in al,60h ;read whatever is at keyboard port
aaa
jz mainloop ;Jump if zero
The above are somewhat flaky due to different hardware, VMs, and emulators not honoring flags correctly.
