函數名: kbhit 
功  能: 檢查當前按下的鍵 
用  法: int kbhit(void); 
程序例: 

#include <conio.h> 

int main(void) 
{ 
   cprintf("Press any key to continue:"); 
   while (!kbhit()) /* do nothing */ ; 
   cprintf("\r\nA key was pressed...\r\n"); 
   return 0; 
} 
  
  
  

函數名: keep 
功  能: 退出并繼續駐留 
用  法: void keep(int status, int size); 
程序例: 

/***NOTE: 
   This is an interrupt service routine.  You 
   can NOT compile this program with Test 
   Stack Overflow turned on and get an 
   executable file which will operate 
   correctly.  Due to the nature of this 
   function the formula used to compute 
   the number of paragraphs may not 
   necessarily work in all cases.  Use with 
   care!  Terminate Stay Resident (TSR) 
   programs are complex and no other support 
   for them is provided.  Refer to the 
   MS-DOS technical documentation 
   for more information.  */ 
#include <dos.h> 
/* The clock tick interrupt */ 
#define INTR 0x1C 
/* Screen attribute (blue on grey) */ 
#define ATTR 0x7900 

/* reduce heaplength and stacklength 
to make a smaller program in memory */ 
extern unsigned _heaplen = 1024; 
extern unsigned _stklen  = 512; 

void interrupt ( *oldhandler)(void); 

void interrupt handler(void) 
{ 
   unsigned int (far *screen)[80]; 
   static int count; 

/* For a color screen the video memory 
   is at B800:0000.  For a monochrome 
   system use B000:000 */ 
   screen = MK_FP(0xB800,0); 

/* increase the counter and keep it 
   within 0 to 9 */ 
   count++; 
   count %= 10; 

/* put the number on the screen */ 
   screen[0][79] = count + '0' + ATTR; 

/* call the old interrupt handler */ 
   oldhandler(); 
} 

int main(void) 
{ 

/* get the address of the current clock 
   tick interrupt */ 
oldhandler = getvect(INTR); 

/* install the new interrupt handler */ 
setvect(INTR, handler); 

/* _psp is the starting address of the 
   program in memory.  The top of the stack 
   is the end of the program.  Using _SS and 
   _SP together we can get the end of the 
   stack.  You may want to allow a bit of 
   saftey space to insure that enough room 
   is being allocated ie: 
   (_SS + ((_SP + safety space)/16) - _psp) 
*/ 
keep(0, (_SS + (_SP/16) - _psp)); 
return 0; 
}