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Calling Functions

Calling Functions

Learn how to invoke functions.

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Calling refers to how a function is used in a code, i.e., how a function is invoked.

Coding example

Let’s take a look at how functions that have already been made are called in the main function.

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#include <iostream>
using namespace std;
void voidFunction();    // declaring a void function
int getSum(int, int);   //declaring a function that takes two int arguments and returns their sum
int main()
{
    int sum;
    voidFunction();        //calling the function with the void return type.
    sum = getSum(2,3);    // calling the function getSum and saving the value returned in variable 'sum'
    cout << "The value of sum is: " << sum << endl;
    return 0;
}
void voidFunction()      // writing the function definition
{
    cout << "This is a void function!" << endl;  // function only prints a string
}
int getSum(int num1, int num2)    // writing the function definition 
{
    //the value 2 has been passed as num1
    //the value 3 has been passed as num2
    return num1 + num2;      // returning the sum of num1 and num2
}

Explanation

  • First note the use of the two declarations that precede the main function. They allow main to use voidFunction and getSum even though they aren’t defined until after main.

  • The forward declarations ensure that the compiler knows that when it sees the symbols ...