Modular Programming

(functions)

Anand Kr. Srivastava

Assistant Professor

Learning Objectives

Explain the concept of modular program design

Explain the concept of a function in C

Explain why functions are important in programming

Explain the structure of a function

Return data type

Parameters

Apply the concept of a function to a practical problem

Explain the Advantage of using Functions.

Modular Programming

Break a large problem into smaller pieces

Smaller pieces sometimes called „modules‟ or

„subroutines‟ or „procedures‟ or functions

Why?

Helps manage complexity

Encourages re-use of code

Allows independent development of code.

How?

First Define the different Module of a given task

independently. Then integrate them into a single

program.

Advantage of Using Modular Programming

( Function).

Re-usability of Code: Re-usability of code without re-

defining.

Reduce the Space Complexity as well as Time

Complexity.

Make the Simpler Program.( Editing , Updating is

easy in Given Program).

Easier to Understand.

Functions

Functions are the set of instructions/lines to complete

the particular task.

Functions are The „building blocks‟ of a program

Any program is a combination of one or more then

one Functions(Modules).

Following Syntax shows the existence of function

concept.

return_type function_name( parameter);

Category of Function

1. Pre-defined Function: Which are already defined

in C library. we can use these function as it is by

their name.

Ex: printf(),scanf(),getch(),clrscr(),main()……

2. User-Defined Function: These functions are

defined by user by their own task. and then user can

use. it can be combination of Predefined and user

defined.

Ex: and(),sub() , etc….

Functions - Mathematical View

32)( 2 xxxf

11 is )2(

113443)2(2)2()2( 2

f

f

f(2)? isWhat

)(xf2 11

XFunction

Returned

value

How to use predefined Function:

In C programming Language, Predefined functions

are defined in corresponding Header files( .h files).

When we use the predefined function, we have to

add the corresponding header file for their definition

with following syntax:

#include<header file Name>

Ex: #include<stdio.h> for

printf(),scanf()….predefined functions.

When compiler get any function in the execution of program,

it jumps on the definition of function( in case of predefined

function, it jumps into the corresponding header file).

How to use user defined Function:

- Step-1 Declaration of function:

Syntax: return_type Function_name(parameter);

- Step-2 Definition of function:

Syntax: return_type Function_name(parameter)

{…………..

…………..

}

- Step-3 Calling of function:(use of function)

Syntax: Function_name(parameter);

Return types in function:

int : when function return a integer type value to

main function.

float: when function return a float type value to main

function.

char: when function return a character type value to

main function.

void: when function does not return a value to main

function.

Movement of Execution Control:

Function Declaration ;

( Before the Calling)

return_type Function ()

{

------------------------

--------------------------

--------------------------

--------------------------

--------------------------

}

Main Body/Block Function Body/Block

void main()

{

---------------------------;

---------------------------;

---------------------------;

Function call();

Jump

Back

--------------------------;

--------------------------;

--------------------------

}

This is called Inter-communication

between functions.

Communication with data in between main () to

other function():

Case 1. main function calls a user-defined function without data.

( Zero parameter & no return type)

Case 2. main function calls a user-defined function with some value.

(transfer a value from main body to function body).-

using function parameter concept. ( parameter & no return type)

Case 3. any user defined function transfer a value to main function-

using return type concept with return statement.

( Zero parameter & some return type)

Case 4. main function send the data to function & function also send

the data to main function.

using function parameter & return type concept

( some parameter & some return type)

Case-1 ( Function have Zero parameter & No return type)

#include<stdio.h>

#include<conio.h>

void Table();

void main()

{

Table();

getch();

}

void Table()

{

int n;

printf(“Enter the No\n”);

scanf(“%d”,&n);

for(int i=1;i<=10;i++)

{

int z=n*i;

printf(“%d*%d=%d”,n,i,z);

}

}

W.A.P. to Print the table of a given No

Case-2 ( Function have parameter & No return type)

#include<stdio.h>

#include<conio.h>

void Table(int x);

void main()

{

int n;

printf(“Enter the No\n”);

scanf(“%d”,&n);

Table(n);

getch();

}

void Table(int x)

{

for(int i=1;i<=10;i++)

{

int z=x*i;

printf(“%d*%d=%d”,x,i,z);

}

}

W.A.P. to Print the table of a given No

Case-3 ( Function have parameter & some return type)

#include<stdio.h>

#include<conio.h>

int Fact();

void main()

{

int n;

printf(“Enter the No\n”);

scanf(“%d”,&n);

int y=Fact();

printf(“Factorial is %d”,y);

getch();

}

int Fact()

{

int n,z=1;

printf(“Enter the No\n”);

scanf(“%d”,&n);

for(int i=1;i<=n;i++)

{

z=z*i;

}

return z;

}

W.A.P. to calculate the factorial of a given No

Case-4 ( Function have parameter & some return type)

#include<stdio.h>

#include<conio.h>

void Table(int x);

void main()

{

int n;

printf(“Enter the No\n”);

scanf(“%d”,&n);

int y=Table(n);

printf(“factorial is %d”,y);

getch();}

int Fact(int x)

{

int z=1;

for(int i=1;i<=n;i++)

{

z=z*i;

}

return z;

}

W.A.P. to calculate the factorial of a given No

Exercise:

- W.A.P Display Fibonacci Series up to 5th Level( Term) using function in

following Situation:

1. Staring values & level will be in user defined function body.

2. Staring values & level will be in main function body

-W.A.P to check weather a given no is Prime or not using function.

- W.A.P to find all Prime no in between 1 to 100 using function.

Example: Calculate Factorial of a given No.#include<stdio.h>

#include<conio.h>

int fact(int n); Declaring the fact method( function)

void main()

{

int x;

printf(“Enter the no”);

scanf (“%d”,&x);

int z = fact(x); Calling fact();

printf(“Factorial of %d is %d”,x,z);

getch();

}

int fact( int n)

{

int f; Definition of fact function

for(int i=1;i<=n;i++)

f= f*I;

return f;

}

Questions: The keyword used to transfer control from a function back to the calling

function is

(1) switch (2).goto (3).go back (4).return

How many times the program will print "IndiaBIX" ?

#include<stdio.h>

int main()

{ printf("IndiaBIX");

main();

return 0; }

(1)Infinite times (2)32767 times (3)65535 times (4) Till stack overflows

Which of the following code will be infinite loop.

(1) if( ; ; ) (2). for( ; ; ) (3) while( ; ; ) (4) .All the above

The use of „break‟ statement:

(1) to terminate the case in switch statement

(2) to force Immediate termination of a loop. (3) Both A & B. (4) None

At the time of function calling , following things are match:

(1) Function Name ( as declared in declaration & definition)

(2)Function Parameter ( as declared in declaration & definition)

(3) return type ( as declared in declaration & definition)

(4)None (5). Both A & B (6). All A,B,C.

Any C program

(1) must contain at least one function

(2) need not contain ant function

(3) needs input data

(4) none of the above

The purpose of main function is

(1) to stop program execution

(2)to stop algorithm

(3)to start program execution

(4)to start algorithm

int cal_sum(int a,int b);in the above example int at the beginning indicates

(1) name of function

(2)return type of function

(3)both function arguments are integer

(4)none of the above

The purpose of return statement is

(1)to return control back to calling function

(2)to return control and value back to calling function

(3)to return void

(4)to return value to the calling function

The statement used to send back any value to the calling function is

(1) continue

(2)exit

(3)break

(4)return

Any program in c contains atleast

(1) three functions

(2) two functions

(3) one function

(4) zero functions

Actual and formal parameters must agree in

(1) names and data types

(2)number of arguments and data types

(3)names and number of arguments

(4)data types

void funct(void)

the above function declaration indicates

(1) it returns nothing and no arguments

(2)it returns nothing and had arguments

(3)it returns a value and had arguments

(4)it returns a value and noa rguments

If the number of actual arguments are not matching with formal arguments

then (1) no error (2)compiler error (3)logical error (4)syntax error

The names of actual parameters and formal parameters

(1) almost same (2)should be same (3)always same (4)need not be same

Any function can be called from any other function. this statement is

(1)neither true nor false (2)true (3)false (4)true some times

A function can be called in a program

(1) only one time (2)only once (3)any number of times (4)only three times

Recursion means

(1) fuction calling a same function (2)fuction with out a return value

(3)function calling a function (4)passing a function to a function

Thanks