我的代码有问题，我不确定我是否写对了

Question

so i'm practicing c and i built a program that says if its prime number or not and i tried to execute it but it wont work it doesnt shows me the output oh and im still new to this i started learning c one week ago.

i dont know how to fix this.

#include <stdio.h>

void Num();

int main()
{
  void Num();

  return 0;
}

void Num()
{
  int n, i, flag = 0;

  printf("Enter a num: ");
  scanf("%d", &n);

  for(i = 1; i <= 10; i++)
  {
    for(n = 1; n <= 10; n++)
    {
      flag = 1;
    }
  }

  if( flag == 1)
  {
    printf("its not the prime num ");
  } else{
    printf("its the prime num" );
  }
}

it wont even show the printf output

Answer 1

You need to go back to the basics (this means: reading a good C book before diving in). You are confusing declaration and calling of functions.

int main()
{
  void Num();

  return 0;
}

main contains two statements:

1. A local (re)declaration of Num as a function without return value.
2. A return statement.

Since you want to call Num rather than redeclaring it, you need to use the function call syntax:

int main()
{
  Num();
  return 0;
}

This is just the first step, however. Your Num function does not perform the correct actions to determine primality.