函数名: bioscom 
 功  能: 串行I/O通信 
 用  法: #include <bios.h> 
         int bioscom(int cmd, char abyte, int port); 
 程序例: 
#include <bios.h> 
 #include <conio.h> 
#define COM1       0 
 #define DATA_READY 0x100 
 #define TRUE       1 
 #define FALSE      0 
#define SETTINGS ( 0x80 | 0x02 | 0x00 | 0x00)
int main(void) 
 { 
    int in, out, status, DONE = FALSE; 
   bioscom(0, SETTINGS, COM1); 
    cprintf("... BIOSCOM [ESC] to exit ...\n"); 
    while (!DONE) 
    { 
       status = bioscom(3, 0, COM1); 
       if (status & DATA_READY) 
   if ((out = bioscom(2, 0, COM1) & 0x7F) != 0) 
      putch(out); 
   if (kbhit()) 
   { 
      if ((in = getch()) == '\x1B') 
         DONE = TRUE; 
      bioscom(1, in, COM1); 
   } 
    } 
    return 0; 
 }