Constants are the terms that cannot be change during program execution. Constants can be classified as :

### Integer constants

Integer constants are the constants in which there is no any fractional part.

### Rules for Constructing Integer Constants

- 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 signed precedes an integer constant, it assumed to be positive.
- No commas or blanks are allowed within a integer constant.
- The allowable range for integer constants is -32768 to 32767.

### Floating-point constants

Fractional constants are the constants that have either fractional part or exponent form.

### Rules for Constructing Real/Float Constants

- A real constant must have at least one digit.
- It must have a decimal point.
- It could be either positive or negative.
- Default sign is positive.
- No commas or blanks are allowed within a real constant.

### Character constants

A character constant is a single alphabet, a single digit or a single special symbol enclosed with single inverted commas i.e. ‘a’, ‘1’, ‘$’.

### Rules for Constructing Character Constants

- A character constant can only have a single digit, alphabet, or a special symbol.
- It must enclosed within single inverted commas. Both the inverted commas should point to the left.
- The maximum length of a character constant can be 1 character.

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