function and their types in C++

In this page we will discuss about C++ function and their Parameters type with following,

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Function in C++

In simple way, The function is a set of statements.

let’s explore it,

It is not easy to manage many statements together in a single program, so we divided these into small pieces or modules. These set of statements (which contain the code to perform a particular task) are called from the other part of the program. These modules are called function.

Function declaration in C++

Declaring a function in name in C++ are called function-Declaration.

Here is the syntax of Declaring a function in C++,

return-type function-name(parameter-list);

Here the function-name is an identifier i.e. any appropriate name to the function while parameter-list are data types.

C++ Function definition

This is the main body of the function in which the code is written to perform a task, we call the definition of any function to the other part of the program. We can also call a function multiple times in the program as per our requirement.

Remember here, we can not call a function without its function definition if we do this a error will be occur in the program at run-time (not compile-time) known as Linker error.

use of function in C++

• The program can be easily read.
• Easy debugging of program.
• There is no need to write an extra statement to perform the same task, ie these can be reuse to perform the same task. which saves time.
• Because using the function does not have to be written repeatedly for the same task, so the size of the program is reduced which increases the speed of the program.

Type of function in C++

• inbuilt functions
• user-defined functions

inbuilt Functions in C++

such functions are already defined in the library of C ++, we can use them by including them in the header file program! The use of inbuilt function in a program makes the program easy, meaning that we do not need to code separately for any task. For example-

 system(“pause”) used to hold the  output on the screen.

user defined function in C++

These are the function that programmers create themselves to perform a task. Their definition consists of a code or set of statement to perform a task. In C++ we can declare the function in three ways which are as follows-

 no argument and no return type function

when we declare the function without parameter-list, these are also called void type functions, because, in the function declaration, void declare inside the bracket in the function header whoever does not return any value.

syntax

void function-name(void);

Here is the program , where void sum(void); is function type

#include<iostream>
using namespace std;
void sum(void); // function declaration

 int main()
  {
    sum(); //function calling
   return 0;
  }

  void sum() // function definition
   {
      int num1,num2,total; // variable declaration

      cout<<"Enter two number: ";
      cin>>num1>>num2;

      total=num1+num2;
      cout<<"Total of these Number: "<<total;
   }

OUTPUT

Enter two number: 5 6
Total of these number: 11

argument but no return type function

This type of functions defines some parameters (data type) inside the bracket in their header while making the function declaration, because their return-type is void type data-type so they do not return any value.

syntax

void function-name(data-type);

Here is the program,

#include<iostream>
using namespace std;
void sum(int,int);          // function declaration

 int main()
  {
    int num1,num2; // variable declaration

    cout<<"Enter two number: ";
    cin>>num1>>num2;

    sum(num1,num2); // function calling
return 0;
  }

  void sum(int x,int y) // function definition
    {
       int total;
       total=x+y;

       cout<<"Total of these Number: "<<total;
    }

OUTPUT

Enter two number: 7 8
Total of these number: 15

argument and return type function

In this type of function declaration, we first declare return data type (except for void), then second function-name and in the last we declare some parameters in parenthesis bracket. These values return. which can be of type int, char or float These functions are not void types.

syntax

data-type function-name(data-type);

Here is the program,

#include<iostream>
using namespace std;
 int sum(int,int); // protoype declaration

int main()
  {
   
     int num1,num2,total; // variable declaration
     cout<<"Enter two number: ";
     cin>>num1>>num2;

     total=sum(num1,num2); // function calling

     cout<<"Total of these Number: "<<total;
   return 0;
  }

  int sum(int x,int y) // function definition
   {
      return x+y;
    }

OUTPUT

Enter two number: 6 8
Total of these number: 14

actual parameter in C++

The parameters declared in the calling function-header  (inside the parenthesis bracket) are called actual parameters.

syntax

function-name(parameter-list);

Example

calculate(a,b);

a and b are called actual parameters.

see the diagram below,

 

formal parameter in C++

Parameters defined in the function definition-header(inside the p) are called formal parameter.

syntax

function-name(parameter-list)
  {
     Body of function;
  }

Example

calculate (int x , int y)
  { 
     body of function;
  }

Here x and y are formal parameters.

Let’s try with an example

#include<iostream.h>
using namespace std;
 void calculate(int,int); // function declaration

 int main()
  {
    
    int a,b; // variable declaration

    cout<<"Enter two number: ";
    cin>>a>>b;

      calculate(a,b); // function calling (actual parameter)
return 0;
  }
  
  void calculate (int x,int y) // function definition (formal parameter)
   {
      cout<<"\nmultiplication: "<<x*y;
      cout<<"\naddition : "<<x+y;
      cout<<"\nsubstraction : "<<x-y;
   }

OUTPUT

Enter two number: 4 5
multiplication: 20

addition : 9
substraction : -1

Things to know

Function is a method that provides the facility to reuse the code to perform the same task, whereas code from control statement is written for a task. Therefore it is important to understand the control statement closely. Data Structure is based on control statement, array and pointer.

Related exercise

• Find out a structure size in C++
• structure with function in C++
• Function with switch statement in C++

more about function,

• Add Array Element Total in C++
• Passing entire Array to a Function C++?
• Passing Array elements Function in C++ 
• Recursion type function in C++
• Parameter Passing  in C++

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