Constants

    Constants are the terms that can't be changed during the execution of a program. For example:

1, 2.5, "Programming is easy." etc.

 

In C, constants can be classified as:

 

• Integer constants

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     Integer constants are the numeric constants

(constant associated with number) without any fractional part or exponential part. There are three types of integer constants in C language:

decimal constant(base 10), octal constant(base 8) and hexadecimal constant(base 16) .

Decimal digits: 0 1 2 3 4 5 6 7 8 9

Octal digits: 0 1 2 3 4 5 6 7

Hexadecimal digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F.

For example:Decimal constants: 0, -9, 22 etc

Octal constants: 021, 077, 033 etc

Hexadecimal constants: 0x7f, 0x2a, 0x521 etc

 

     Notes:You can use small caps a, b, c, d, e, f instead of uppercase letters while writing a hexadecimal constant.Every octal constant starts with 0 and hexadecimal constant starts with 0x in C programming.

 

• Floating-point constants

     Floating point constants are the numeric constants that has either fractional form or exponent form. For example:-

2.0 0.0000234 -0.22E-5

 

Note:Here, E-5 represents 10-5.

Thus, -0.22E-5 = -0.0000022.

 

Character constants

     Character constants are the constant which use single quotation around characters.

For example:

'a', 'l', 'm', 'F' etc

 

Escape Sequences

     Sometimes, it is necessary to use newline(enter), tab, quotation mark etc. in the program which either cannot be typed or has special meaning in C programming. In such cases, escape sequence are used.

 

For example:

\n is used for newline.

The backslash( \ ) causes "escape" from the normal way the characters are interpreted by the compiler.

 

Escape Sequences CharacterS

• \bBackspace

• \fForm feed

• \nNewline

• \rReturn

• \tHorizontal tab

• \vVertical tab

• \\Backslash

• \'Single quotation mark

• \"Double quotation mark

• \?Question mark

• \0Null character

 

String constants

     String constants are the constants which are enclosed in a pair of double-quote marks.

For example:

"good" //string constant "

" //null string constant "

" //string constant of six white space "x" //string constant having single character. "Earth is round\n"

//prints string with newline

 

Enumeration constants

     Keyword enum is used to declare enumeration types. For example:enum color {yellow, green, black, white};Here, the variable name is color and yellow, green, black and white are the enumeration constants having value 0, 1, 2 and 3 respectively by default.

    For more information about enumeration, visit page: Enumeration Types.