### C Constants

- Constant in C language are also the name given to the data values stored in memory like variable but the value of constant cannot be changed at the time of execution.
- There are several types of Constants in C. They are classified in the two groups as given below in the figure:

#### Numeric Constants

Numeric constants can be of two types Integer and real constants:

##### Integer Constants

- Integer constant are sequence of number from digits 0 to 9 without any decimal point or fractional parts.
- Integer constants can be positive or negative.
- The number without any sign assumed to be positive number.
- Integer constants can be of minimum 2 bytes and maximum 4 bytes.
- Here are some examples of Integer constants:

45, -16, +56, 67 etc.

##### Real Constants

- Real constant are also known as floating point constants which contains decimal point as well as fractional parts.
- Real constants can be positive or negative.
- The number without any sign assumed to be positive number.
- Real constants can be written in exponential notation which contains two parts mantissa and exponent.
- The mantissa and exponent part are separated by a letter e.
- Mantissa is a real number represented in decimal or integer it can be positive or negative. Whereas exponent is an integer number that can be positive or negative.
- Here are some examples of real constants:

+2.7, -3.8, 6.7, 4.5 etc

+1.5e+6

-3.8e6

3.4e-7 etc.

+1.5e+6

-3.8e6

3.4e-7 etc.

#### Character Constants

Character constants can be categorized into two parts:

##### Single Character Constants

- A single character constant can be a alphabet, digit or special symbol enclosed in single quote.
- Single character requires only one byte.
- Here are some examples of single character constants:

'A', 'b', '@', '8' etc.

##### String Constants

- String constants in c are sequence of characters enclosed in double quotes.
- Here are some examples of string constants:

"Ram", "Good","1234", "@@@@"

### Declaration of Constants

- You have to declare the constant before using it into the program.
- Constant is declared using the keyword 'const'.
- Here is the syntax for declaring constant in C.
- Some examples of declaring constant in C++ are given here:
- Here is an example of using constant in C program:
- The output of the above program is as follows:

const data-type constant_name=data_value;

const int a=10;

const float b=10.34;

const char c='a';

const float b=10.34;

const char c='a';

```
#include<iostream.h>
```

int main()

{

const int a=10;/*constant declaration*/

printf("\nvalue of a is:%d",a);

return 0;

}

value of a is:10