From Newsgroup: alt.bbs.pcboard

DOS keyboard polling in Windows can be tricky. How to avoid hogging the
CPU with bioskey() polling while at the same time giving the DOS program
enough horsepower is a question of some interest to me.

Typically the polling is too fast and hogs the CPU, or too slow and the
program can't get much work done. I spent some time tinkering with this,
and here is a solution I found.

It runs best with maximum idle sensitivity. You can copy the _default
shortcut (.pif extension is hidden) from the Windows directory, rename
it to match the .exe you build, and change its properties; that gives
you a custom .pif file.

Trying to retrofit this technique into PCBoard looks difficult though. I
may never get that far ...


# include <stdio.h>
# include <dos.h>
# include <bios.h>
# include <time.h>

static int tick[2];

void interrupt
ticktock (void)
{
tick[0] = 1;
}

int
main (void)
{
static int key;
static unsigned long count;
static FILE *file;
static char *fn = "z.txt";
static void interrupt (*int1c) (void);
static time_t now;

file = fopen (fn, "w");
if (!file) {
fprintf (stderr, "failure opening %s\n", fn);
goto fail;
}

int1c = getvect (0x1c);
setvect (0x1c, ticktock);

for (count = 0; count < 20000; ++count) {

now = time (NULL); /* secret ingredient */
if ((key = bioskey (1)) != 0) {
if (key == -1 || bioskey (0) == 0x011b) {
break;
}
}

disable ();
tick[1] = tick[0];
tick[0] = 0;
enable ();

if (tick[1]) {
tick[1] = 0;
fprintf (file, "count = %lu, time = %ld\n", count, now);
}

}

done:
if (int1c)
setvect (0x1c, int1c);
return 0;

fail:
if (int1c)
setvect (0x1c, int1c);
return 1;
}
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