Datatypes

 

There are 4 basic data types used in C :

  1. integer

  2. floating point

  3. double precision

  4. character

 Integer

 

Any positive or negative number without a decimal point.

 

Examples of valid integer constants are :

3        -20             +890   -3896

 

Integers may be signed (having a leading + or -) or not signed .

 

Not allowed with integer:

  1. commas

  2. decimal points

  3. special symbols

Examples of invalid integers

$23.09       2,456   3.0    

 

Compilers have limits on the largest and smallest integer values that can be used .These limits are implementation dependant ;they depend on how much storage each compiler sets aside for an integer .

 

Floating point and Double Precision Numbers

 

Any signed or unsigned numbers having a decimal point.

 

Examples

+12.121    5.  -4.9     0.0

 

Not allowed

  1. commas

  2. special symbols

Examples if invalid numbers

5,324.88     24       $56.4

 

Most computers use twice amount of the storage for double precision numbers than for floating point numbers.

 

Exponential Notation

 

Floating point and double precision numbers can be written in exponential notation which is commonly used to express either very large or very small numbers in a compact form.

 

Examples

 

Decimal Notation

Exponential Notation

1234.

1.234e3

54321.

5.4321e4

0.00987

9.87-e3

.000215

2.15-e4

 

The letter e stands for exponent .The number following the e represents a power of 10 and indicates the number of places the decimal point should be moved to obtain the standard decimal value.

 

Character

 

Characters are letters of the alphabet (uppercase and lowercase) , the ten digits 0 through  9 and special symbols such as + %$ # @ !* .

 

A single character is any one letter ,digit or special symbol enclosed by single quotes .

 

Examples are

'A'    '#'     'b'   'Y'   '!'

 

Character constants are typically stored in a computer using either the ASCII ( ASK-KEY ) or ANSI (ANN-SEE) codes .

 

ASCII stands for American Standard Code for Information Interchange.

 

ANSI stands for American National Standards Institute is an extended set of 256 codes , the first of which are the same as the ASCII codes .

 

Each of these codes assigns individual characters to a specific pattern of 0's and 1's.

 

Letter

Code

a

01100001

b

01100010

c

01100011

 

Using the ASCII code the sequence of characters 'a' ,'b' , 'c' requires 3 bytes of storage .

 

01100001

01100010

01100011

a

b

c

 

Escape Sequences

 

The combination of a backslash and a specific characters.

 

When a backslash ( \ ) is used in front of a selected group of characters , the backslash tells the compiler to escape from the way these characters would normally be interpreted .

 

Each of these combination have only one character code .

 

Escape Sequence

Name

Meaning

\a

Alert

Produces an audible or visible alert.

\b

Backspace

Moves the cursor back one position (non-destructive).

\f

Form Feed

Moves the cursor to the first position of the next page.

\n

New Line

Moves the cursor to the first position of the next line.

\r

Carriage Return

Moves the cursor to the first position of the current line.

\t

Horizontal Tab

Moves the cursor to the next horizontal tabular position.

\v

Vertical Tab

Moves the cursor to the next vertical tabular position.

\'

 

Produces a single quote.

\"

 

Produces a double quote.

\?

 

Produces a question mark.

\\

 

Produces a single backslash.

\0

 

Produces a null character.

 

 

Data Types (32-bit)

Type Length Range
data type bits from to
unsigned char 8 0 255
char 8 -128 127
short int 16 -32,768 32,767
unsigned int 32 0 4,294,967,295
int 32  -2,147,483,648 2,147,483,647
unsigned long 32 0 4,294,967,295
enum 16 2,147,483,648 2,147,483,647
long 32 -2,147,483,648 2,147,483,647
float 32 3.4 x 10-38  3.4 x 10+38
double 64 1.7 x 10-308 1.7 x 10+308
long double 80 3.4 x 10-4932 1.1 x 10+4932
near (pointer) 32 bits not applicable

far (pointer) 32 bits not applicable