C++ Functions

  • A function is a group of statements that together perform a task.
  • Every C++ program has at least one function, which is main(), and all the most trivial programs can define additional functions.
  • You can divide up your code into separate functions.
  • How you divide up your code among different functions is up to you, but logically the division usually is so each function performs a specific task.
  • A function declaration tells the compiler about a function's name, return type, and parameters.
  • A function definition provides the actual body of the function.
  • A function is knows as with various names like a method or a sub-routine or a procedure etc.


return_type function_name( parameter list )
   body of the function

A C++ function definition consists of a function header and a function body. Here are all the parts of a function:

Return Type:

  • A function may return a value.
  • The return_type is the data type of the value the function returns.
  • Some functions perform the desired operations without returning a value.
  • In this case, the return_type is the keyword void.

Function Name:

  • This is the actual name of the function.
  • The function name and the parameter list together constitute the function signature.


  • When a function is invoked, you pass a value to the parameter.
  • This value is referred to as actual parameter or argument.
  • The parameter list refers to the type, order, and number of the parameters of a function.
  • Parameters are optional; that is, a function may contain no parameters.

Function Body:

  • The function body contains a collection of statements that define what the function does.


#include <iostream>
// function declaration
int max(int num1, int num2);
int main ()
// local variable declaration:
int a = 99;
int b = 97;
int ret;
// calling a function to get max value.
ret = max(a, b);
cout << "Max value is : " << ret << endl;
return 0;
// function returning the max between two numbers
int max(int num1, int num2) 
// local variable declaration
int result;
if (num1 > num2)
result = num1;
result = num2;
return result; 


Max value is : 99


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