C Functions

C Functions basics

A function in C is self-contained block of statement that perform a single meaning full task

A c program is made up of many function and among them that must be main

If program is complex it divides in number of small program is called function


Classification of function in C

Function are classified in two types:

  1. Library or built function
  2. User define function (UDF)

Library function

The function which are already written and are provide as a part of language are called library function

Example: - Printf(),scanf(),getch(),clrscr() etc


User Defined Function

The function which are written by programmer for some specific purpose other than library function is called user defined functions.


Need or benefit of user defined functions

A user defined function is required for following purposes:

  • if a program is to large and complex it divide in function
  • in such situation we can write a function which can be use repeatedly which will help us to save time and minimize the size of programe
  • it become easy to find error in the program else it is divide into function
  • write once and use multiple time

Defining of function

The general form of a function definition in C programming language is as follows –

     return type function name (parameter list)


         Body of the function



A function definition in C programming consists of a function header and a function body. Here are all the parts of a function:

  • Return Type − A function may return a value. The return type is the data type of the value the function returns. Some functions perform the desired operations without returning a value. In this case, the return type is the keyword void.
  • Function Name − This is the actual name of the function. The function name and the parameter list together constitute the function signature.
  • Parameters − A parameter is like a placeholder. When a function is invoked, you pass a value to the parameter. This value is referred to as actual parameter or argument. The parameter list refers to the type, order, and number of the parameters of a function. Parameters are optional; that is, a function may contain no parameters.
  • Function Body − The function body contains a collection of statements that define what the function does.

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