# Constant in C++ | Literals in C++

## What is a constant in C++?

It is a quantity whose value we can’t change during the execution of program. They are of two types.

• Numeric Constant
• Character Constant

## Numeric Constant

Numeric Constants contain digits only. They are of two types

• Integer Constant
• Floating point Constant

## Integer Constant in C++

Integer Constants can contain numeric values without decimal point in them.

They are of three types.

1. Decimal Integer Constant
2. Octal Integer Constant

### Decimal Integer Constant

It contains digits from 0 to 9. So its base is 10

Examples:  6, 45, 5467 etc.

Examples of Invalid Decimal Integer constant are

16,62    //Comma not allowed.

3.6      //Decimal point not allowed

3   33  // Can\t contain space.

\$24       //Can’t contain special characters

### Octal Integer Constant

It contains digits from 0 to 7. Its base is 8.

Example:  0123, 06663

Examples of invalid Octal Integer Constants are

058      //Can’t contain  8.

It contains digits from 0 to 9 and alphabets from A to F. where

A = 10

B = 11

C = 12

D = 13

E = 14

F = 15

Its base is 16. Hexadecimal Number starts with 0X.

Example: 0X23, 0X6f9A

Examples of invalid Hexadecimal Integer Constants are

11.5      //Can’t contain decimal point]

## Floating point Constant in C++

Floating point constants contain numbers with decimal point.  They can be used to represent very small as well as very large quantities.

Real constants can be used in two ways

• Standard Form
• Exponent Form

### Standard Form

In this form, floating point number contains digits followed by a dot (.) further followed by digits called fractional part.

Examples:  12.33 ,     3.5,      -1.5 ,     +5.0,     .55,

### Exponent Form

This type of floating point number  is represented in terms of power of 10.

Power of 10 is represented by alphabets E or e .

There are two parts of number in exponent form.

• Mantissa: Digits before the alphabet E.
• Exponent: Digits after the alphabet E. It can only contain integers.

Examples

1.45 х 105  can be represented as 1.45E5

3.5590  х 10-2  can be represented as 3.5590e-2

Examples of invalid floating point  constants in Exponent form

1.45E2.5   //Exponent Part contains floating point Number

4.55e  4       //Exponent Part contains space between 3 and 4.

## Character Constant in C++

Character Constant in C++ can store alphabets, digits, special symbols as well as blank spaces.

They are of three types

• Single Character
• String
• Escape Sequence

### Single Character Constant in C++

It contains a single alphabet, digit, special character or space within single quotes.

Examples:  ‘A’ , ‘8’ , ‘\$’,  ‘@’

### String Constant in C++

It  contains multiple characters within double quotes (Inverted commas “).

String constant always ends with a special character known as null represented as ‘\0’

Examples:  “Aman” , “2022” , “\$600”,  “[email protected]” etc.

“Aman” is a string constant that contains 5 characters  as there are four characters  in string “Aman” and one character is for null character \0.

### Escape Sequence in C++

These are special character constants to represent non graphical characters in C++. Most common non graphical characters include enter key, backspace, tab etc.

They start with a backward slash ( \  ) followed by a specific character.

Most commonly used escape sequences in C++ are:

1)  \n

To insert one blank line where it  appears.

```#include<iostream>
using namespace std;
int main()
{
cout<<“Welcome”;
cout<<“\nBye “;
return 0;
}```

Output:

```Welcome
Bye```

2)  \t

To leave a gap of 8 spaces.

```#include<iostream>
using namespace std;
int main()
{
cout<<“Welcome \t Bye “;
return 0;
}```

Output

`Welcome       Bye`

3)  \b

To delete a character appearing before it.

```#include<iostream>
using namespace std;
int main()
{
cout<<“Welcome\b Bye “;
return 0;
}```

Output:

Welcom Bye

4)   \\

Shows backward slash( \ ).

```#include<iostream>
using namespace std;
int main()
{
cout<<“Welcome\\ Bye “;
return 0;
}```

Output:

`Welcome\ Bye`

5  \’

Shows Single Quotes (‘) .

```#include<iostream>
using namespace std;
int main()
{
cout<<“Father\'s name “;
return 0;
}```

Output:

`Father's name`

6) \”

Shows Double Quotes ( ) .

```#include<iostream>
using namespace std;
int main()
{
cout<<"\"Welcome\"";
return 0;
}```

Output:

`"Welcome"`

7) \0   (Back Slash followed by zero)

To terminate a string. Nothing after it will be shown.

```#include<iostream>
using namespace std;
int main()
{
cout<<“Welcome\0 Bye “;
return 0;
}```

Output:

`Welcome`