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Constants or Literals in C?

Constants_or_Literals_in_C

Constants or Literals in C

Constants are the fixed values that never change during the execution of a program. Following are the various types of constants:

C Constants

  • C Constants are also like normal variables. But, only difference is, their values can not be modified by the program once they are defined.
  • Constants refer to fixed values. They are also called as literals
  • Constants may be belonging to any of the data type.
  • Syntax:

const data_type variable_name; (or) const data_type *variable_name;

TYPES OF C CONSTANT:

  1. Integer constants
  2. Real or Floating point constants
  3. Octal & Hexadecimal constants
  4. Character constants
  5. String constants
  6. Backslash character constants
Constant type
data type (Example)
Integer constants int (53, 762, -478 etc )
unsigned int (5000u, 1000U etc)
long int, long long int
(483,647 2,147,483,680)
Real or Floating point constants float (10.456789)
doule (600.123456789)
Octal constant int (Example: 013 /*starts with 0 */)
Hexadecimal constant int (Example: 0x90 /*starts with 0x*/)
character constants
char (Example: ‘A’, ‘B’, ‘C’)
string constants
char (Example: “ABCD”, “Hai”)

Constant in C, Types of Constant in C - C Tutorial

RULES FOR CONSTRUCTING C CONSTANT:

1. INTEGER CONSTANTS IN C:

  • An integer constant must have at least one digit.
  • It must not have a decimal point.
  • It can either be positive or negative.
  • No commas or blanks are allowed within an integer constant.
  • If no sign precedes an integer constant, it is assumed to be positive.
  • The allowable range for integer constants is -32768 to 32767.

2. REAL CONSTANTS IN C:

  • A real constant must have at least one digit
  • It must have a decimal point
  • It could be either positive or negative
  • If no sign precedes an integer constant, it is assumed to be positive.
  • No commas or blanks are allowed within a real constant.

3. CHARACTER AND STRING CONSTANTS IN C:

  • A character constant is a single alphabet, a single digit or a single special symbol enclosed within single quotes.
  • The maximum length of a character constant is 1 character.
  • String constants are  enclosed within double quotes.

4. BACKSLASH CHARACTER CONSTANTS IN C:

  • There are some characters which have special meaning in C language.
  • They should be preceded by backslash symbol to make use of special function of them.
  • Given below is the list of special characters and their purpose.
Backslash_character Meaning
 Backspace
f Form feed
New line
Carriage return
Horizontal tab
Double quote
Single quote
\ Backslash
v Vertical tab
a Alert or bell
? Question mark
N Octal constant (N is an octal constant)
XN

Hexadecimal constant (N – hex.dcml cnst)

CONSTANTS Constants are also known as literals in C. Constants are  quantities whose values do not change during program execution. There are  two types. - ppt download

HOW TO USE CONSTANTS IN A C PROGRAM?

1) C const keyword

 

The const keyword is used to define constant in C programming.

  1. const float PI=3.14;  

Now, the value of PI variable can t be changed.

#include    

int main(){    

    const float PI=3.14;    

    printf("The value of PI is: %f",PI);    

    return 0;  

}  

   

Output:

The value of PI is: 3.140000

If you try to change the the value of PI, it will render compile time error.

#include    

int main(){    

const float PI=3.14;     

PI=4.5;    

printf("The value of PI is: %f",PI);    

    return 0;  

}    

 

Output:

Compile Time Error: Cannot modify a const object

2) C #define preprocessor

The #define preprocessor is also used to define constant. We will learn about #define preprocessor directive later.

Let s see an example of #define to create a macro.

#include   

#define MIN(a,b) ((a)<(b)?(a):(b))  

void main() {  

   printf("Minimum between 10 and 20 is: %d ", MIN(10,20));    

}  

 

 

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