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  C++ Programming Tutorials
Basics of C++

Structure of a program
Variables Data types
Basic Input/output

Control Structures
Control Structures
Functions (I)
Functions (II)

Compound Data Types
Character Sequences
Dynamic Memory
Data Structures
Other Data Types

Object Oriented Programming
Classes [I]
Classes [II]
Friendship & Inheritance

Advanced Concepts
Type Casting
Preprocessor Directives

C++ Standard Library
Input/output with Files

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C++ Programming Tutorials

Functions with no type. The use of void.
If you remember the syntax of a function declaration:

type name ( argument1, argument2 ...) statement

you will see that the declaration begins with a type, that is the type of the function itself (i.e., the type of the datum that will be returned by the function with the return statement). But what if we want to return no value?

Imagine that we want to make a function just to show a message on the screen. We do not need it to return any value. In this case we should use the void type specifier for the function. This is a special specifier that indicates absence of type.

// void function example
#include <iostream>
using namespace std;

void printmessage ()
cout << "I'm a function!";

int main ()
printmessage ();
return 0;
I'm a function!

void can also be used in the function's parameter list to explicitly specify that we want the function to take no actual parameters when it is called. For example, function printmessage could have been declared as:

void printmessage (void)
cout << "I'm a function!";

Although it is optional to specify void in the parameter list. In C++, a parameter list can simply be left blank if we want a function with no parameters.

What you must always remember is that the format for calling a function includes specifying its name and enclosing its parameters between parentheses. The non-existence of parameters does not exempt us from the obligation to write the parentheses. For that reason the call to printmessage is:

printmessage ();

The parentheses clearly indicate that this is a call to a function and not the name of a variable or some other C++ statement. The following call would have been incorrect:


NEXT >> Functions (II)

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