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Functions

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Definition

A function is a group of statements that

performs some kind of task.

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3 essential things about Function

function prototypecan be thought of as

specifying its interface

Function callingwhen a function is being

called by some other function

function definition specifies what a function

does.

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Advantages of Functions

Less code duplication

easier to read

Easier to update programs Easy to find out errors--each function can be

verified separately

Reusable codethe same functions can be used in different programs

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Syntax of Function

Return_type function_ name (arguments)

{

Body of function Return value;

}

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Program of additionWITHOUTusing

Functions

#include #include

Void main()

{

Int a , b, c;

Scanf(%d%d, &a,&b);

c=a+b;

Printf(value of c= %d,c);

}

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Scenario 1

Main function will call another function to do

its own task.

For example--- main function will call add

functionto do the addition and display the

result

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Program of additionusing Functions

#include

#include

Void add(); // function declaration Void main()

{

Add(); // calling of add function

}

Void add() // function definition

{

Int a , b, c; Scanf(%d%d, &a,&b);

c=a+b;

Printf(value of c= %d,c);

}

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Doing the additionMORE THAN ONE

TIMEin the same program

without_function.doc

http://localhost/var/www/apps/conversion/tmp/scratch_6/without_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/without_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/without_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/without_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/without_function.doc

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Using Function

using_function.doc

http://localhost/var/www/apps/conversion/tmp/scratch_6/using_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/using_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/using_function.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/using_function.doc

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Calling Function & Called function

In previous example,

Main function is the Calling function----who ismaking a call to add function

Add function is said to be called functionwho is responsible for actually performing the

addition of two numbers

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Main function --------------is the master

Add function -------------is the slave , who isperforming some task.

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Scenario 2

Main function will call another function to doits own task + main function wants to printresult of its own.

For example--- main function will call addfunctionto do the addition,now after doing

addition the result is sent back to mainfunction , then main function will displaythe result.

U S

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Use o returnStatement

#include

#include

intadd(); // function declaration Void main()

{

Int basket;

basket=Add(); // calling of add function

Printf(value of addition = %d, basket);

}

intadd() // function definition

{ Int a , b, c;

Scanf(%d%d, &a,&b);

c=a+b;

return c;

}

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Another example

Find out the greater number among two

numbers using Functions , if a>b then

calculate the Quotient , otherwise set answer

=0.

grtr_without using return.docx

using return statement

using_return.doc

http://localhost/var/www/apps/conversion/tmp/scratch_6/grtr_without%20using%20return.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/using_return.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/using_return.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/grtr_without%20using%20return.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/grtr_without%20using%20return.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/grtr_without%20using%20return.docx

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Disadvantage of return statement

We can only ONE value from one function toanother function

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Program to check whether a given number is

EVEN or ODD using Function

chk_even_odd.docx

http://localhost/var/www/apps/conversion/tmp/scratch_6/chk_even_odd.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/chk_even_odd.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/chk_even_odd.docxhttp://localhost/var/www/apps/conversion/tmp/scratch_6/chk_even_odd.docx

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Scenario 3

Earlier responsibility of main function is just

to call another function.

Another function is responsible for-----------

Taking the input of two numbers

doing the addition of numbers.

BUT NOW , main function wants to takeinput of two numbers of its own ,wants to

pass these numbers to another function.

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How to pass values from one

function to another

Either using

------------Call by VALUE

Or using

------------Call by REFERENCE / Call by ADDRESS

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What is parameter/ argument

Passing values from one function to another

function ---------------is said to be PARAMETER

or ARGUMENT.

TWO TYPES of parameter/ argument-----

ACTUAL PARAMETER----used at the time of

function calling

FORMAL PARAMETER-----used at the time of

function definition

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What is call by VALUE & call by

REFERENCE

In call by value , we pass the actual values

at the time of function calling.

In call by reference, we pass addressinstead of values, at the time of function

calling.

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Local variable & Global Variable

Local variables------------

----------------are limited to one block.

----------------its value does not exist in any

other function.

-------------by default value is garbage

Global Variable-----------

--------------- are used in whole program

---------------by default value is zero

---------------its value persists for entire program

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Addition of two numbers using call

by VALUE

call_value.doc

http://localhost/var/www/apps/conversion/tmp/scratch_6/call_value.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/call_value.doc

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Area of circle using Call by VALUE

and using RETURN

call_value_return.doc

Program of factorial using FUNCTIONS

http://localhost/var/www/apps/conversion/tmp/scratch_6/call_value_return.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/call_value_return.doc

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Program of factorial using FUNCTIONS # include

#include

int fact(int a);

Void main()

{

Int z, basket;

scanf(%d, &z);

basket= Fact(z);

Printf(factorial is=%d , basket);

}

Int fact(int a)

{

Int i, ans=1;

For (i= 1; i

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Scenario 4

Instead of passing values as arguments,

Pass the ADDRESSES of variables , at the time

of function calling.

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POINTER

It is a special type of variable,

which contains the address of any other

variable , instead of value.

int * p;

Int q; P= &q;

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Addition of two numbers using call

by REFERENCE

call_ref.doc

http://localhost/var/www/apps/conversion/tmp/scratch_6/call_ref.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/call_ref.doc

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Area of circle using Call by REFERENCE

and using RETURN

call_ref_return.doc

S NO call by value call by reference

http://localhost/var/www/apps/conversion/tmp/scratch_6/call_ref_return.dochttp://localhost/var/www/apps/conversion/tmp/scratch_6/call_ref_return.doc

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S. NO. call by value call by reference

1. Values are passed at the

time of function

Address is passed at the

time of function

2. No use of pointer use of pointer

3. Simple , easy to

understand

Complicated, difficult to

learn

4. Also knows as downward

communication

Also knows as upward

communication

5. NO need to worry about

the memory addresses

User must know about

the concepts of the

memory addresses

6. ( IMPORTANT) Changes made in

function will not

reflected back in main

function

Changes made in

function will reflected

back in main function

Swapping of two numbers using CALL BY VALUE

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Swapping of two numbers using CALL BY VALUE

#include

#include

Void swap(int a, int b);

Void main()

{

Int a, b;

Scanf(%d %d, &a , &b);

Swap(a,b);

Printf(value of a= %d \n value of b= %d, a, b);

}

Void swap(int a, int b)

{

Int temp;

Temp=a;

a=b;

b=temp;

Printf(value of a= %d \n value of b= %d , a, b);

}

Swapping of two numbers using CALL BY REFERENCE

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Swapping of two numbers using CALL BY REFERENCE

#include

#include

Void swap(int *a, int *b); Void main()

{

Int a, b;

Scanf(%d %d, &a , &b);

Swap(&a,&b); Printf(value of a= %d \n value of b= %d, a, b);

}

Void swap(int *a, int *b)

{

Int temp;

Temp=*a;

*a=*b;

*b=temp;

Printf(value of a= %d \n value of b= %d , *a, *b);

}

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Recursion

A function can call itself either directly or

indirectly.

We can use recursion , where we want to

execute the same set of instructions,

repeatedly.

Factorial of a number using RECURSION

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Factorial of a number using RECURSION #include

#include

int fact(int a);

void main()

{

int z,ans;

scanf("%d", &z);

ans=fact(z);

printf("factorial is = %d", ans);

}

int fact(int b)

{

int ans;

if(b==0)

return 1;

else

return b*fact(b-1);

}

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