FUNCTIONS of C program (PART-1)

Hello friends....!!!! welcome back ..!! We studied important topic of C language in previous post which is pointer. Now I came with new post which name is functions. Here we will discuss about basic knowledge in deep. So here we will start from definition. So here we go.

FUNCTION:

            Function is a collection of statement known by particular name which performs some well defined task.

Types of function:

1)    User defined function

2)    Library function

Functions that are created by programmer is called USER DEFINED FUNCTIONS. Functions which are already available in library are called as LIBRARY FUNCTIONS. Function reduces the size of code, when it is used in program. Function called its self is called recursion.

            In user defined function, function is defined by the programmer in the program. When the size of program is increase, it produces difficulty to understand and maintain. When some part of the code is repeated in the program, we can write that portion of the code as a function. so result is function reduces the size of code and convert complex program into easy form.

            Library function is already available inside of the library of C. They are divided into different categories according to their uses. For example, for string process we use string.h header file, for mathematical functions, we use math.h header file. 

FUNCTION DECLARATION:

            type function name(argument);           /* syntax */

type means type of value returned. Function name is name of user defined function. Argument means arguments supplied to the function. If there are no arguments in the bracket then the bracket left empty. In last function is terminated by semicolon (;) symbol.

  

FUNCTION DEFINITION:

            type function name (arguments)

            {

            Statement; 

             }

In the functions, there are three points to be noted. First is declaration, Second is call and third is definition. let us learn one by one.

In definition, function name, type, and arguments have same meaning as declaration. But in this point one portion is added as the statement with "{}" symbols. And main point is that semicolon (;) is not allowed after arguments but it allows after statement. Because function declaration is like user defined function so we have to include semicolon (;) and function definition is like library function so it is already in library so semicolon (;) is not necessary.

For function call let see this program.

#include<stdio.h>

#include<conio.h>

void printnumber()                   /* declaration */

main()

{

    clrscr();

    printnumber();                      /* call */

    getch();

}

void printnumber()                     /* definition */

{

printf(" HELLO \n");

}

In above program,

 void printnumber();

is declaration function. It tells the compiler that some where in the program printnumber will be encountered.

void printnumber()

{

    printf(" Hello\n");

}

is the definition function. When above function is called, message will be printed on screen which is Hello.

printnumber();  is a call to the printnumber() function so the statements in the body of function will be executed.

In above program, we added a declaration part. But it is not necessary to write declaration part in all the program. Declaration is not needed if the definition function is written above the call of the function.

TYPES OF FUNCTIONS BASED ON ITS SYNTAX:

•  No arguments and no return value
•  With arguments and with return value
•  With arguments and no return value

 Here we learnt no arguments and no return value. When we add arguments, we need to know about formal variable and actual variable before understanding 2^nd and 3^rd types.

“Variables which are used in the definition function are called formal variables. Variable which are used in the call to the function are called as actual variable.”

Following program is helpful to understand this topic.

 In this program,

 int sum(int x, int y);

     is declaration of sum function. Here x and y are formal variables because these are used in declaration function. When a call to the function is made in main() function, the actual parameters are passed, for example:     

ans=sum(x,y);

this line calls the function ans, with variable x ,y. the variables x and y work as actual variable.

we can not call the function as                                                 

sum(x,y);       because the function returns integer.

            So guys, this is part one of functions. Part two will be in my next post. I am sure that your concept will be clear. Read this concept remember it and use this in the program. If there is any doubt, please feel free to mention it in the comment box. If you are interested you may join our 

facebook group new age informers.

To Like Our Facebook Page > NewAgeInformers 
To Subscribe Our Youtube Channel > Wolfpack

Until then bye bye...!!!!!