What does mean from calling function or calling program?

Answer 1

After defining function, we need to call it to execute that function and get results..
Ex:
void add(int n, int m)
{
printf("%d", n+m);
}
Now we can call this like
add(2,5);
Output we get is 7

Answer 2

A  calling function is a request made by a program or script that performs a predetermined function.

Answer 3

After a function definition it is supposed to be called to perform its specific task.for example we can create a function that add two integers and output its results when involved.
#include<iostream>
Using namespace std;
Int add( int a,int b)
{int c;
c=a+b;
return c;
}
int main()
{
int m,n=39;
G=add(m,n);
cout<<G<<endl;
return 0;
}