What is a function?

Functions are nothing but sub-programs of a program .

Is a part of a program which performs a particular task as desired by the programmer.

It can be called anywhere in the program.

S. Kiran PGT(Comp. Science), KV, Malleswaram

Functions exhibit the feature of MODULARITY in OOP (Object Oriented programming).

What is Modularity?

The act of breaking up larger programs into smaller unit is called modularity.

S. Kiran PGT(Comp. Science), KV, Malleswaram

Advantages of using Functions

Easier to maintain, update and debug.

Enhances readability of the program

Reusability of code

S. Kiran PGT(Comp. Science), KV, Malleswaram

TYPES OF FUNCTIONS

BUILT – IN FUNCTIONS

USER DEFINED FUNCTIONS

S. Kiran PGT(Comp. Science), KV, Malleswaram

BUILT – IN FUNCTIONS

These are part of the compiler package, which are defined in the standard library files also called header files.

For e.g..,string.h header file contains definition for the following functions.strlen(), strcmp(), strrev () etc.

S. Kiran PGT(Comp. Science), KV, Malleswaram

USER DEFINED FUNCTIONS

Are functions defined by the programmer.

That is YOU.

S. Kiran PGT(Comp. Science), KV, Malleswaram

FUNCTION DEFINITIONA function must be defined before it is used

anywhere in the program.

Three important things that must be remembered

1. Function prototype2. Function call3. Function Definition

S. Kiran PGT(Comp. Science), KV, Malleswaram

FUNCTION PROTOTYPE

It has the following parts1. Return type2. Function Name3. Parameters or Argument list

For e.g.:int sum ( int x, int y) ;

Return type

Name

Argument List

Function prototype must end with a semi

colon

S. Kiran PGT(Comp. Science), KV, Malleswaram

FUNCTION DEFINITION AND CALL#include<iostream. h> int square ( int n)#include<conio.h> {void main() return n x n;{ }

clrscr();int square(int);int a, s;cout<<“Enter value for a”;cin>>a;s = square(a);cout<<“Square of given no. is”<<s;getch();

}

S. Kiran PGT(Comp. Science), KV, Malleswaram

prototype

Func. call

Function definition

S. Kiran PGT(Comp. Science), KV, Malleswaram

S. Kiran PGT(Comp. Science), KV, Malleswaram

S. Kiran PGT(Comp. Science), KV, Malleswaram

S. Kiran PGT(Comp. Science), KV, Malleswaram

S. Kiran PGT(Comp. Science), KV, Malleswaram

Note: A function prototype is not required if the function definition appears before its calling function

Program

S. Kiran PGT(Comp. Science), KV, Malleswaram

RECAPITULATION

S. Kiran PGT(Comp. Science), KV, Malleswaram

Which feature of OOP does function exhibit?

List the advantages of using functions?

Name the different types of functions.

Three things to remember in a function ______

What does function prototype tell the compiler?

What is meant by return type?S. Kiran PGT(Comp. Science), KV, Malleswaram