lt21.c

programs in <C program design>

# include "stdio.h"
void main( )                   
{
int i=1,sum=1,n;
printf("请输入一个非负整数\n");
scanf("%d",&n);
if (n>0)
while(i<=n)
{
 sum=sum*i;
 i=i+1;
}
printf("%d!=%d\n",n,sum);
}