Functions in C++

  • Every C++ program has at least one function, main().
  • Functions come in two varieties:
    1. 1. Built-in functions, which are part of your compiler package. A great reference are available here.
    2. User-defined functions, which are the functions you write yourself.
    Example of a User-defined function:
    Source code Result
    #include <iostream>
    // function Demonstration Function
    // prints out a useful message
    void DemonstrationFunction() {
      std::cout << "In Demonstration Function\n";
    // function main - prints out a message, then
    // calls DemonstrationFunction, then prints out
    // a second message.
    int main() {
      std::cout << "In main\n" ;
      std::cout << "Back in main\n";
      return 0;
    In main
    In Demonstration Function
    Back in main

    You can download this example here (needed tools can be found in the right menu on this page).

  • Functions return a value or they return void, meaning they do not return anything.
  • Functions consist of a header, which will be the name and any included parameter to the function, and a body, which will be the code inside the function braces.
  • Method is simply another term for functions that are part of a class.
  • Functions can be called by another function which can be called by another function and so on.
  • When a function call has returned any, statement after the call will be executed in you program.
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