- C constants are like normal variables, but the only difference is their value can't be modified by the program once defined.
- Constants have the fixed values.
- The constants are also called as
**Literals**. - Constants may be belonging to any of the datatypes.
- There are a few types of constants;
- Numeric Constant.
- Non-numeric Constant.

## 1. Numeric Constant:

- Numeric constant stands for a number.
- The number can be integer, fraction etc.
- Real numbers are also considered as the numeric constants.
- Real constants are the combination of integer and fraction.

### a. Integer Constant:

- Integers are the natural numbers including zero.
- Integer constants may be decimal, octal, hexadecimal constants.
- Decimal: {0,1,2,3,4,5,6,7,8,9}
- Octal: {0,1,2,3,4,5,6,7,8,9}
- Hexadecimal: {0,1,2,3,4,5,6,7,8,9, A, B,C,D,E,F}
- Integers may be
**Signed Integer**and**Unsigned Integer**. **Signed Integer**refers to the -ve and +ve values including zero.**Unsigned Integer**refers to the +ve values including zero.- The largest integer number that can be stored in a 16-bit computer is 2
^{15}- 1. - The largest integer number that can be stored in a 32-bit computer is 2
^{31}- 1. - The Octal constants are written with a leading zero.
- Ex: 0234
- The Hexadecimal constants are written in a leading 0x.
- Ex: 0x49B

####
__Rules for Integer Constant__:

- An integer constant must have at least one digit.
- It must not have a decimal point.
- It can be either positive or negative.
- If no sign precedes an integer constant, it is assumed to be positive.
- Commas or blanks are not allowed within an integer constant.

### b. Floating-Point Constant:

- A fraction is used for scientific notation or exponent form.
- The floating point number has two parts.
- One is a decimal part and another part is a fractional part.
- While representing in fractional form, we have to include the decimal point.
- And sometimes we have to use
**e**or**E**. - Ex:
- 3.234
- 3234E3
- Both the examples have the same value but presented in two ways.

## 2. Non-numeric Constant:

- Non-numeric constants are the constants except the number.
- The non-numeric constants may be Character or String constants.

### a. Character Constant:

- Character constants are always written in the single quoted form.
- Ex: 's'
- Character constants can be a single character or an escape sequence or a universal character.
- Plain Character: 'a', 'b', 'x' etc.
- Escape Sequence: '\n', '\t', '\a' etc.
- Universal Character: '\u02C0',

### b. String Constant:

- A collection of characters is known as a string.
- These are written in double-quoted form.
- Always a string constant is terminated with a special character called known as null character.
- Ex: "Welcome"

## Constant Defining:

There are two ways to define CONSTANTS in C Programming-- Using
**const**keyword. - Using
**#define**preprocessor.

### a. Using const Keyword:

**Syntax**: const type variablename = value;

**Example**:

#include<stdio.h>

void main()

{

const int op1 = 10;

const int op2 = 15;

int addition;

addition = op1 + op2;

printf("The addition is = %d", addition);

}

**Output**: The addition is = 25

### b. Using #define Preprocessor:

**Syntax**: #define variablename value

- We don't need to put a semicolon (;) for the termination.

**Example**:

#include<stdio.h>

#define op1 10

#define op2 15

void main()

{

int addition;

addition = op1 + op2;

printf("The addition is = %d", addition);

}

**Output**: The addition is = 25

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