这个代码来自C900里的。我看不懂请高人解释下。

#include <stdio.h>
#include <dos.h>
#include <dir.h>

int function[255]; /* DOS services*/

void interrupt far (*original_handler)();

void interrupt far handler(void)
{
char i;

asm { mov i, ah }

function[i]++;

_chain_intr(original_handler);
}

void main(void)
{
int i;

for (i = 0; i < 255; i++)
function[i] = 0;

original_handler = _dos_getvect(0x21);
_disable();
_dos_setvect(0x21, handler);
_enable();

printf("This is a message\n");
fprintf(stdout, "This is a second message\n");

printf("Current disk is %c\n", getdisk() + 'A');

_disable();
_dos_setvect(0x21, original_handler);
_enable();

for (i = 0; i <= 255; i++)
if (function[i])
printf("Function %x called %d times\n", i, function[i]);
}