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:
- Numeric Constants
- Integer Constants
- Real Constants
- Character Constants
- Single Character Constants
- String Constants
- Backslash Character Constants
Integer Constant
It's referring to a sequence of digits. Integers are of three types viz:
- Decimal Integer
- Octal Integer
- 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
Constants | Meaning |
---|---|
\a | beep sound |
\b | backspace |
\f | form feed |
\n | new line |
\r | carriage return |
\t | horizontal tab |
\v | vertical tab |
\' | single quote |
\" | double quote |
\\ | backslash |
\0 | null |