!-- Global site tag (gtag.js) - Google Analytics --> function in c++ - programmingworld

Breaking

function in c++

                            C++ function

 A C++  function is a named unit of a group of program statements. Functions have basically reduced the size of programs.
 A Function always returns a single value.
The Function also should have a return type.

C++ Function Definition

A Function definition is as given below.


type  function_name(parameter list)
{
    The Body of the function;
}

A  function definition must have a return statement.

A  function can also have an ‘open’ parameter list.

Example:-


int data(int p)
{
return(p<0 ? –p: p);
}

C++ Function declaration

A function declaration tells the compiler about a function name and how to call the function.

A function declaration is given as below.


type function_name( parameter list );


With parameter example


int para( int x , int y);

Accessing a c++ function

When a program calls a function, program control is transferred to the called function.

It returns program control back to the main program.

To call a function, you need to pass the required parameters.



#include<iostram.h>

int main1()
{

float cube(float);                //function prototype declared.

float a,b;
cout << “\n Enter number= \n”;

cin >> a;
b= cube(a);                        //call the function and assign.
                                           //it’s return value to variable y.

cout << “\n The cube of” << a << “is “<< a<< “\n”;
returm 0;
}                      //end of main

float cube (float x)
{
float n;
 n= x*x*x*;
return (n);
}                 


Output:-

Enter number
3
The cube of 3 is 27

Types Of Functions:-

Function are two types.

  •      Built-in functions.
  •      User-defined functions.

          1.  Built-in functions:-These functions are part of the compiler package. These are part of the standard library made available by the compiler. Example, exit(), sqrt(), pow(), strlen() etc.are library functions.

          2.    User-defined functions:- The user-defined functions are created by the user. These functions are created as per the requirement of the user program.


Function Prototype :

A function prototype is a declaration of the function that tells the program about the type of the value returned by the function and the number and type of arguments.
                                                  or
A function prototype describes the function interface to the compiler by giving details such as the number and type of arguments and the type of return values.
A general form of function prototype is as shown below:


type function-name ( parameter list );


In a  function prototype, the names of the arguments are optional.

Example :


float  volume (int a, float b, float c);
                    Or
float area (float, float);

Call By Value :

The call by value method copies the values of actual parameters into the formal parameters, that is, the function creates its own copy of argument values and then uses them.


#include<iostream.h>

int main()
{
int change(int);               //prototype declared

int orig1 = 10;
cout <<”\nThe value is”<< orig1 <<\n”;
cout <<”\nReturn value of function () is”<< 
change(orig) <<”\n”;
cout <<”\nThe value after function change is over” << orig <<”\n”;

return 0;
}
int change(int a)

{
a=20;                               //The value is changed.    
return a;                         //The changed value is returned.
}


Output:-

The original value is 10
Return value of function change() is 20
The value after function change() is over 10

Call by Reference :

The call by reference method of passing arguments to a function copies the reference of an argument into the formal parameter.

Incall by the reference method changed made in the formal parameters are reflected back to actual parameters.


#include<iostream.h>
int main()
{
void swap(int &,int &);
                   //function prototype accepting two reference variable.
int a,b;
a=7;
b=4;
cout<<"\nThe original value are:\n";
cout<<"a="<<a<<",b="<<b<<"\n";
swap(a,b);
cout<<"\n The value after swap() are\n";
  cout<<"a="<<a<<",b="<<b<<"\n";
return (0);
}
void swap(int &x,int &y)
{
int temp;
 temp=x;
x=y;
y=temp;
cout<<"\n The swapped values are:\n";
cout<<"a="<<x<<",b="<<y<<"\n";
}



Output:-


The original values are:
a=7, b=4

The swapped value are:
a=4, b=7

The values after swap() are:
a=4, b=7