C Constants

Constants are like a variable, except that their value never changes during execution once defined.

C Constants is the most fundamental and essential part of the C programming language. Constants in C are the fixed values that are used in a program, and its value remains the same during the entire execution of the program.

• Constants are also called literals.
• Constants can be any of the data types.
• It is considered best practice to define constants using only upper-case names.

Constant Definition in C

const type constant_name;

const keyword defines a constant in C.

#include<stdio.h>
void main()
{
    const int SIDE = 10;
    int area;
    area = SIDE*SIDE;
    printf("The area of the square with side: %d is: %d sq. units", SIDE, area);
}

Putting const either before or after the type is possible.

int const SIDE = 10;

or

const int SIDE = 10;

Constant Types in C

Constants are categorized into two basic types, and each of these types has its subtypes/categories. These are:

Integer Constant

It's referring to a sequence of digits. Integers are of three types viz:

1. Decimal Integer
2. Octal Integer
3. Hexadecimal Integer

15, -265, 0, 99818, +25, 045, 0X6

Real constant

The numbers containing fractional parts like 99.25 are called real or floating points constant.

Single Character Constants

It simply contains a single character enclosed within ' and ' (a pair of single quote). It is to be noted that the character '8' is not the same as 8. Character constants have a specific set of integer values known as ASCII values (American Standard Code for Information Interchange).

'X', '5', ';'

String Constants

These are a sequence of characters enclosed in double quotes, and they may include letters, digits, special characters, and blank spaces. It is again to be noted that "G" and 'G' are different - because "G" represents a string as it is enclosed within a pair of double quotes whereas 'G' represents a single character.

"Hello!", "2015", "2+1"

Backslash character constant

C supports some character constants having a backslash in front of it. The lists of backslash characters have a specific meaning which is known to the compiler. They are also termed as "Escape Sequence".

\t is used to give a tab

\n is used to give a new line