Constants and Literals

A constant is a value or an identifier whose value cannot be change during program execution. In other words, you can say variable is fixed value.

For example: 1, 2.5, "C programming is easy" etc.

Value of variable are called literals.

 const double PI = 3.14

Here, PI is a constant. Basically what it means is that, PI and 3.14 is same for this program.

Integer constants

A integer constant is a numeric constant (associated with number) without any fractional or exponential part.

There are mainly three types of integer constants available in C programming

1. decimal constant(base 10) : 0, -7, 8 etc.

2. octal constant(base 8) : 031, 066, 044 etc.

3. hexadecimal constant(base 16) - 0x4f, 0x5a, 0x321 etc.

In C programming, octal constant starts with a 0 and hexadecimal constant starts with a 0x.

Floating-point constants

A floating point constant is a numeric constant that has either a fractional form or an exponent form. For example

Character constants

A character constant use in single quotes. For example: 'a', 'l', 'm', 'F'

Escape Sequences

Sometimes, it is necessary to use characters which cannot be typed or has special meaning in C programming. For example: newline(enter), tab, question mark etc. In order to use these characters, escape sequence is used.

For example: \n is used for newline. The backslash ( \ ) causes "escape" from the normal way the characters are interpreted by the compiler.

String constants

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

Enumeration constants

Keyword enum is used to define enumeration types that means user can define their own data type. For example:

enum subject {C, Html, Java, Sql};

Here, subject is name of variable and C, Html, Java and Sql are the values (enumeration) constants having value 0, 1, 2 and 3 accordingly.