Thread: beginner function questions

Hello all:
I am writing a program for a course assignment. This is the first time I have been exposed to functions in C. Therefore; I am confused about a few things. But here is my code:

Code:

#include <stdio.h>
#include <stdlib.h>

int isPrime(int num)
{
    int i,mods;
    for(i=1;i<=num;i++)
                      {
                          int mod;
                          mod = num &#37; i;
                          if(mod == 0)
                                 { mods = mods+1; }
                          }
    if(mods==2)
              {
                          return 1;
                          }
    else
        {
                          return 0;
                          }  
}

int main(void)
    {
              int inputNum;
              scanf("%d",&inputNum);
              if(isPrime(&inputNum) == 1)
                                   { printf("yes"); }
              else { printf("no"); }
}

This code cannot compile; it gives an error about trying to convert int* to int when i call the isPrime() function with the &inputNum integer.
Is this something to do with pointers? I do not believe we need to use pointers in this program or... do i?
Also; for functions; can I return true/false inside of 0/1?
Or can I use the function to update a variable in main? For ex: I have a number i got from the user in main; but I want to manipulate it with a function and return it. How can I use a function to do that?

Thanks in advanced!!!

As to the rest, you would need to pass the address of the variable to a function, if you want the function to be able to modify it. (Viz: printf doesn't do anything, so it just takes the variable; scanf needs to update the variable, so you have to pass it &var.)

That means that in your function header, you wouldn't want num to be an int, but a pointer-to-int:

Code:

void do_something(int *num);

Then any changes made via indirection (i.e., *num = 6) would be seen in the calling program.

Aha I get it. Sorry for the newb questions; but thanks for helping!