51 single-chip microcomputer realizes single-key repeated keystroke detection

Copyright: 2013-07-27.version1.0
File name: key.c
Description: Self-made single key recognition to achieve repeated key function
Author: 
Version: version1.0
Date: 2013.7.27
History: None
**************************************************************/
#include
sbit key=P0^0;
int num=0;

/****************************************************
Function: delay_press()
Description: The delay function when the key is pressed
Calls: None
Called By: key_test()
Table Accessed: None
Table Updated: None
Input: void 
Output: None
Return: 1->press
     0->release
Others: None
******************************************************/
int delay_press(void)
{
 int press=1;
 int i,j;
 for(i=0;i<255;i++)
  for(j=0;j<255;j++)
   press=1;
 press=0;
 return press;
}

/****************************************************
Function: delay()
Description: Delay function
Calls: None
Called By: key_test()
Table Accessed: None
Table Updated: None
Input: void 
Output: None
Return: void 
Others: None
******************************************************/
void delay(void)
{
 int i,j;
 for(j=0;j<25;j++)
  for(i=0;i<25;i++);
}

/********************************************************
Function: key_test()
Description: Single key recognition function
Calls: delay()
Called By: main()
Table Accessed: None
Table Updated: None
Input: void 
Output: num, press the key once and num will increase by one
Return: void 
Others: None
******************************************************/
void key_test(void)
{
 if(!key)
 {
  delay();
  if(!key)
  {
   num++;
   if(num>255)
   num=0; 
  }
 }while(delay_press()); 
}
/*****************************************************
Function: main()
Description: The main function of the program
Calls: key_test()
Called By: None
Table Accessed: None
Table Updated: None
Input: void 
Output: None
Return: void 
Others: None
******************************************************/
void main(void)
{
 //int i;
 while(1)
 {
  key_test();
  P2=~num; 
 }
}