Function

Key points:

• It is most important tool in a procedural programming.
• A function can be defined as a block of statements which is used to perform any particular task according to requirements.
• The main objective of function is to reduce the complexity of programs.
• In this case a large program can be divided into multiple parts, that part is called function or module.

There are some advantages of function :-

• We can create user friendly program with the help of function. In this case the user can create separate function for each module according to requirements.
• It provides reusability. It means a written source code can be saved multiple times.
• It provides extendibility . It means a program can be modified and extended in future.
• It reduces the complexity of programs.
• It provides readability. It means function oriented program is more readable rather than non function oriented programs.
• Function creates user friendly program because debugging process is easy.

Types of function :-

There are two types of function :

Types of function in C

• Predefined function (inbuilt function)
• User defined function ( customized function )

Predefind function :-

This type of function is already defined in programming language. We cannot change the behaviour of function.

example:-

  
   printf() , scanf() , clrcr() , getch() , strlen() , etc.

User defined function :-

This type of function is created with the help of user according to requirements.

example:-

findarea() , findfact() , even() , etc.

Function prototype :-

• It represents architechture of function.
• It must be required if main function is defined before user defined function.
• It must be written after declaration of header file.

example:-

#include<stdio.h>

void findsum();

void main()

{

   findsum();

 }

void findsum()

 {

   statements;

  }

How to call a function :-

syntax :-

   
  function name();

example :-

 void main()

  {

    findsum();

   }

Function architecture / pattern :-

It represents type of function as return type , non-return type , parameterised or non-parameterised.

There are four architecture of function :-

1. A function with no return type and no parameter / argument.
2. A function with return type but no parameter / arguments.
3. A function with no return type but with parameter / arguments.
4. A function with return type and with parameter / arguments.

How to create user defined function :-

1. function with no return type and no parameter

syntax :-

void <function name> ()

 {

    block of stmts;

   }

function with no return type and no parameter syntax

example :-

 void display()

{

  printf( “ hello” );

 } 

 2. Function with return type but no parameter

syntax:-

   <data type> <function name> ()

{

   block of stmts;

  }

function with return type but no parameter syntax

example:-

 int findadd()

  {

  int a = 10, b = 20 ;

 add = a + b ;

  return (add) ;

}

 Parameter:- 

Parameter is a special variable which can be supplied during a function and calling a function.

    There are two types of parameter:

        1. formal parameter :- Those parameters which are supplied during creating a function called formal parameter . It is treated as local variable.

        2. actual parameter :- Those parameters which are supplied during  calling a function.  It is also called as argument.

3. A function with no return type but with parameter

  

syntax:-

void <function name> ( <data type> <parameter 1>, ..)

 {

  block of stmts;

  }

function with no return type but with parameter syntax

 example:-

 void findadd( int a, int b)

{

   int add ;

  add = a + b;

  printf( “ addition = %d “, add);

 }

4. A function witth return type and with parameter

syntax:-

 <data type> < function name > ( parameter list )

 {

   block of stmts;

   return (variable);

 }

function with return type and with parameter syntax

P.example:- Program to input any no. after that find factorial value using function.

#include<stdio.h>

#include<conio.h>

void findfact()

 {

  int a, fact=1 , i ;

 printf( “ enter the no “ );

 scanf( “ %d “, &a );

  for ( i = 1 ; i <= a ; i ++ )

  {

    if( a % i == 0 )

   fact = fact * i ;

  }

 printf( “ factorial = %d “, fact );

}

void main()

 {

  clrscr ();

 findfact ();

getch ();

 }

We practice more program on this topic on the next blog.