请教高手做一C语言

#include<iostream>
using namespace std;
int fun(int);
int main()
{
int i,sum;
for(i=2,sum=0;i<=100;i++)
if(fun(i)) sum=sum+i;
cout<<"100以内的素数和是:"<<sum<<endl;
return 0;
}
int fun(int n)
{
int i,count;
for(i=2,count=1;i<=n/2;i++)
if(n%i==0) {count=0; break;}
return count;
}

#include <stdio.h>
void main()
{
int i, j, sum = 0;
int flag;
int a[50];
for (i = 2; i < =100; i+=2)
{
flag = 0;

for (j = 2; j <= i / 2; ++j)
{
if (i % j == 0)
{
flag = 1;
break;
}
}
if (!flag)
a[sum++] = i;
}
printf("%d\n", sum);
for (i = 0; i < sum; ++i)
printf("%d ", a[i]);
putchar('\n');
}

#include<stdio.h>

void main()