20131003国庆作业例4-4,4-5,4-6.

#include<stdio.h>
int main(void)
{
int i,m;

printf("Enter a number:");
scanf("%d",&m);
for(i=2;i<=m/2;i++)
if(m%i==0)
break;
if(i>m/2&&m!=1)
printf("%d is a prime number!\n",m);
else
printf("No!\n");

return 0;
}

#include<stdio.h>
int main(void)
{
int mynumber=38;
int count=0,yournumber;
for(count=1;count<=5;count++){
printf("Input your number:");
scanf("%d",&yournumber);
if(yournumber==mynumber){
printf("Ok!you are right!\n");
break;
}
else
if(yournumber>mynumber)
printf("Sorry!your number is bigger than my number!\n");
else
printf("Sorry!your number is smaller than my number!\n");
}
printf("Game is over!\n");

return 0;
}

#include<stdio.h>
double fact(int n);
int main(void)
{
int i;
double sum;
sum=0;
for(i=1;i<=100;i++)
sum=sum+fact(i);
printf("1!+2!+...+100!=%e\n",sum);

return 0;
}
double fact(int n)
{
int i;
double result;

result=1;
for(i=1;i<=n;i++)
result=result*i;

return result;
}