C Basics

Constants in C

A constant as the name suggest is something which does not change during its life time.


In C, a constant is basically an entity whose value once defined will never change during the program execution.

A C constant will hold its value firmly through every stage of program life cycle and would not let it change at any cost. C constants are also referred as literals.


A C constant can be classified as two types:

  1. Number constant 
  2. Character constant

C Constant by tutorialsinhand.com


We can declare various types of constant in C as shown below:

Number Constant

  • integer constant,
  • decimal constant,
  • floating-point constant


  • An integer constant is made up of sequence  of digit
  • Digits can be any digits from 0-9 preceded by “+ or –“ sing
  • The integer constant can be represented as octal no. are hexadecimal number
  • An octal integer consist of any combination of digits from 0-7 with a leading 0
  • A sequence of digits preceded by OX or ox is considered as hexadecimal integer
  • A hexadecimal integer is combination of digits from 0-9 and alphabets A to F or a-f


  • Real constant are values which have fractional part
  • Integer number are not to sufficient to represent to values which change continues like distance , price , height , temperature  etc.
  • In such case real constant are use
  • Real constant are also called floating point constant

Character Constant

  • character constant,
  • string literals

Character constant:-

  • Character constant are divided into two types
  • Single character constant:-
  • A single character constant contains only one character inclosed within pair of single quotation
  • Each character constant has an integer values associated with it called ASCII values (American standard  code for information interchange)
  • Where A=65 and a=97

String character constant:-

  • The string character constant is a sequence of characters (more than one character) inclosed with double quotation mark
  • The character may be alphabets, digits, symbol, and blank space.

Backslash character constant:-

  • We may also use special backslash character constants.
  • These constant are combination of backslash and a character enclosed within single quotes as shown below:

\n →  new line

\t  →   horizontal tab

\a  →   audible

\v  →    vertical tab

\    →    single slash

\\   →    double slash

|    →    double quotes

\r   →    carriage return

\f    →   form feed


Define Constant in C

C allows defining constant by two ways:

  1. Through #define preprocessor
  2. Through const keyword




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