C发声程序

#include "stdafx.h"
#include <stdio.h>
#include <windows.h>
#include <math.h>
#include <conio.h>
typedef struct {
      short int pitch;
      short int duration;
} NOTE;
NOTE notes[] = {{14, 500}, {16, 500}, {12, 500}, {0, 500}, {7, 1000}};
void setfreq(int hz)
{
       hz = 1193180 / hz;      // clocked at 1.19MHz
       _outp(0x43, 0xb6);      // timer 2, square wave
       _outp(0x42, hz);
       _outp(0x42, hz >> 8);
}
void playnote(NOTE note)
{
      _outp(0x61, _inp(0x61) | 0x03);   // start speaker going
      setfreq((int)(400 * pow(2, note.pitch / 12.0)));
      Sleep(note.duration);
      _outp(0x61, _inp(0x61) & ~0x03);  // stop that racket!
}
int main(int argc, char* argv[])
{
     int i;
     HANDLE h;
     h = CreateFile("\\\\.\\giveio", GENERIC_READ, 0, NULL,
     OPEN_EXISTING, FILE_ATTRIBUTE_NORMAL, NULL);
     if(h == INVALID_HANDLE_VALUE)
     {
           printf("Couldn't access giveio device\n");
           return -1;
     }
     for(i=0; i < sizeof(notes)/sizeof(int); ++i)
           playnote(notes[i]);
     CloseHandle(h);
     return 0;
}
有几点需要注意：
1，\\\\.\\giveio是打开的设备，由于是用\\转义表示\，所以上述其实是表示\\ . \
2，这种底层的编程很少。以上_outp访问的是底层寄存器，功能如注