3-4.c

一些简单的c51程序

#include <REG52.H>
#include <stdio.h>
void main (void) 
{
	int month;
	int day;
	SCON = 0x50; 
TMOD |= 0x20; 
TH1 = 0xf3; 
TR1 = 1;
TI = 1; 
	
	printf("please input the month number :");
	scanf("%d",&month ) ;
	switch (month)
	{
		case 1:
		case 3:
		case 5:
		case 7:
		case 8:
		case 10:
		case 12: day=31;
				break;
		case 4:
		case 6:
		case 9:
		case 11:day=30;
				break;
		case 2: day=28;
			break;
		default : day=-1;
	}
	if(day==-1)
	printf("Invalid month input !\n");
	else
	printf("1999.%d has %d days \n",month,day);
    while (1) {};
}