Constants in C

A Presentation

On

Department of Computer & Information Technology,

M.S.P.V.L. Polytechnic College,

Pavoorchatram.www.ustudy.in

Introduction A constant is a quantity whose value does not

change during programming execution. There

are three types of constants they are

Numeric constant

Character constant

String constant

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Numeric constant A numeric constant is a constant made up of

digits and some special characters. There are

two types of numeric constants. They are

Integer or fixed point constant

Real or floating point constant

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Integer constant Integer constant is a constant made up of digits

without decimal point. This can have values from -

32,708 to +32,627

Rules

An integer constant is formed with digits 0 to 9.

The constant can be preceded by + or – sign.

No special characters are allowed anywhere in the

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Real Constant The numbers with decimal point are called real constant or

floating point constant.

A real constant is formed with the digits 0..9 and a decimal point.

The number can be preceded by + or –

The digits before and after the decimal point can be omitted.

No white spaces or special characters are allowed.

Floating point constants can be represented with f for floating and

l for double precision floating point numbers.

The real constants can be expressed in two forms

a) Fraction form

b) Exponential form

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a)Fractional Form:

The number is written with one decimal point

Example:

2.1567 .761 -34.7 are valid real number in fractional form.

b) Exponential form:

This is useful for representing very large or very small numbers in

magnitude. The general form is

Mantissa e or E exponent

Example:

The number 215.65 can be written in exponent notation as

2.1565e2

The number -0.0000375 can be written as -3.75e-5www.ustudy.in

Character Constant

There are two types of character constants.

They are

Direct

Escape sequence

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Single character constant:

A single character constant consists of a single character

enclosed within single quotes. The single character

constants are stored in memory using their ASCII

equivalent. So every character constant has an integer

value corresponding to its ASCII value. For example the

character 'A' has the equivalent integer ASCII value 65.

Example:

‘$’ ‘e’ ‘9’ are character constants

Here ‘9’ is not equal to numeric 9.

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Escape Sequences

The Escape Sequences are special characters for

formatting. Character combinations consisting of

a backslash (\) followed by a letter or by a

combination of digits are called "escape

sequences." These special printing characters are

used to make the output readable when printing

characters to the screen, file, or other device

(such as printer).www.ustudy.in

Character for Bell (Alert) is .........................'\a'.

Character for Backspace is .........................'\b'.

Character for Horizontal Tab is ...................'\t'.

Character for Vertical Tab is .......................'\v'.

Character for Newline (Line Feed) is ..........'\n'.

Character for Form Feed is .........................'\f'.

Character for Carriage Return is ................'\r'.

Character for Quotation Mark is .................'\"'.

Character for Apostrophe is .......................'\''.

Character for Question Mark is ...................'\?'.

Character for Backslash is ..........................'\\'.

Character for Null is ...................................'\0'.

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String Constant

A string constant is a sequence of characters

enclosed within double quotation marks. This

can be formed with digits, alphabets and

special characters.

Example:

“C Program” “!Hello****” are valid

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