Calling a function from another file

Hello, im having trouble using a function from another file in a project,
this is a example from my book:
Calling a function with only a prototype:

Code:

#include <iostream>

using namespace std;

void BigDog(int KibblesCount);

int main()
{
    BigDog(3);
    return 0;
}

Using a function from a seperate file:

Code:

#include <iostream>

using namespace std;

void BigDog(int KibblesCount)
{
    cout << "I'm a lucky dog" << endl;
    cout << "I have " << KibblesCount << " pieces of food" << endl;
}

i know how this example works but, i tried making my own:

I make a prototype and made the function:

Code:

#include <iostream>
using namespace std;

int Sum(int x,int y);

int main(){
cout << "Type 2 numbers" << endl;
cout << Sum(30,20) << endl;
}
int Sum(int x,int y){

 int result;

 result = x + y;
 return result;
    
}

Here i tried making the file where i was going to use the Sum(int x,int y) function:

Code:

#include <iostream>

using namespace std;

int Sum(int x,int y)
{
    cout << "The number is " << Sum(x,y) << endl;
}

but i dont know how to program this file so it'll be able to use the Sum function.

Any help?

What IDE are you using? If you use Visual C++ or CodeBlocks, just add a new header and source files (a .h and a .cpp files) into the project. And then in your main source file (ie. the one with your "int main()" block), insert an include statement of the header file (eg. #include "foo.h") and you're all set. However, if you are using vi or notepad for this (well I know some people who swear that vi is da bomb :P ), you need to manually link the files yourself.

Originally Posted by g4j31a5

What IDE are you using? If you use Visual C++ or CodeBlocks, just add a new header and source files (a .h and a .cpp files) into the project. And then in your main source file (ie. the one with your "int main()" block), insert an include statement of the header file (eg. #include "foo.h") and you're all set. However, if you are using vi or notepad for this (well I know some people who swear that vi is da bomb :P ), you need to manually link the files yourself.

i just reread my book and now i get it LOL, i should read slower next time ;P