Ok, Im not sure what a stresser program is...but I think I can help.

When declaring a data type, the arguments can vary. So you could have a void function with three int passed to it. Or a float function with three int passed to it. Declaring the type of fuction tells the computer which data type you will return. So if you do have a float function with three int passed to it, just make sure you are returning a float and not an int, or else it will give you an error.

Yes, you can have as many fuctions as you want. That is what is great about functions, they make your code neat and organized.

Code:
//Test
#include<iostream>

using namespace std;

void this_function(int, int);
float that_function(int, int);

int main()
{
    float x;
    this_function(1,2);
    x = that_function(3,4);
    cout<<x<<endl;
    return 0;    
}

void this_function(int a, int b)
{
    int x;
    x = a + b;
    cout<<x<<endl;
    return;    
}

float that_function(int a, int b)
{
    float x;
    x = (a+b)*2;
    return x;    
}
I hope that helps.

-Ep