3-14.c

一些简单的c51程序

#include <REG52.H>              
#include <stdio.h>                
#include <math.h>
void main (void) {

	int j,n,p,q,flagp,flagq;
	
	SCON = 0x50; 
TMOD |= 0x20; 
TH1 = 0xf3; 
TR1 = 1;
TI = 1; 
	
	printf("please input n :");
	scanf("%d",&n);
	if (((n%2)!=0)||(n<=4))
		printf("input data error!\n");
	else
	{
		p = 1 ;
		do {
			p = p + 1 ;
			q = n - p ;
			flagp=1;
			for(j=2; j <= (int)(floor(sqrt((double)(p))));j++)
			{
				if ((p%j)==0)
				{
					flagp=0;
					break;
				}
			}
			flagq=1;
			for (j=2;j<=(int)(floor(sqrt((double)(q))));j++)
			{
				if ((q%j)==0)
				{
					flagq= 0 ;
					break;
				}
			}
		} while (flagp*flagq==0);
		printf("%d = %d + %d \n",n,p,q);
	}
    while (1) {};
}