Constant in C Language


  • 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 constant in C language:

    1. Integer constants
    2. Real or Floating point constants
    3. Octal & Hexadecimal constants
    4. Character constants
    5. String constants
    6. Backslash character constants
S.no
Constant type
data type
Example
1Integer constantsint
unsigned int
long int
long long int
53, 762, -478 etc 
5000u, 1000U etc
483,647
2,147,483,680
2Real or Floating point constantsfloat
doule
10.456789
600.123456789
3Octal constantint013          /* starts with 0  */
4Hexadecimal constantint0×90        /* starts with 0x */
5character constants
 char
‘A’   ,   ‘B’,     ‘C’
6string constants
char
“ABCD”   ,   “Hai”

Rules for constructing constant in C Programming:

1. Integer Constants in C language:

    • 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 language:

    • 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 language:

    • 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 language:

    • 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_characterMeaning
\bBackspace
\fForm feed
\nNew line
\rCarriage return
\tHorizontal tab
\”Double quote
\’Single quote
\\Backslash
\vVertical tab
\aAlert or bell
\?Question mark
\NOctal constant (N is an octal constant)
\XNHexadecimal constant (N – hex.dcml cnst)

How to use constants in a C language program?

    • We can define constants in a C program in the following ways.
  1. By “const” keyword
  2. By “#define” preprocessor directive
    • Please note that when you try to change constant values after defining in C program, it will through error.

1. Example program using const keyword in C:

Output:

value of height : 100
value of number : 3.140000
value of letter : A
value of letter_sequence : ABC
value of backslash_char : ? 




2. Example program using #define preprocessor directive in C language:

Output:

value of height : 100
value of number : 3.140000
value of letter : A
value of letter_sequence : ABC
value of backslash_char : ?










www.cinterviews.com appreciates your contribution please mail us the questions you have to cinterviews.blogspot.com@gmail.com so that it will be useful to our job search community

No comments:

 
Top Blogs