Variables and Data Types in C

What is Variable?

Variable is the name of memory location which can store a single value
Variable is an identifier (name) for storing a value
In C before using variables they must be declared.

C Programming Building blocks:

Character Set: combination of letters (a-z) numbers (0-9) and symbols used in C Programming are Character Set, it is just like alphabet in our languages.
Keywords: reserved words which have pre-defined meaning, these words can not be used as identifiers.
Identifiers: Names of any any thing such as Variable name , function name etc are called Identifiers.
Constants: Any entity whose value can not be changed after execution are called Constants.
Variables: Names which store values
Datatypes: They keywords such as int, float, char are called datatypes they are used to create Variables, they denotes the kind of data a variable can store, size of variable and range of values a variable can store.
Format Specifies: The characters such as %d, %i, %f, %u are called format specifies they indicates the format of data which is to be displayed through some output function such as printf and the format of data which is to be entered through input function such as scanf()
Escape Sequences: Escape sequences are characters such as \n, \t, \r, \b, \x, \o which breaks the sequence of any string.
Expressions: The combination of operators and operands for some computation are called expressions.
Assignments: The expressions which are used to assign some value to an other variable.
Functions: Any unit of program which perform some task.
Operators: Any symbol such as +, - , *, / which perform some operation on values called operands.

How to declare Variables in C:

• In C Programming before using Variables they must be declared.

Syntax:

<Data Type> Identifiers

• Data Type: Data types represent the type / kind of Data a variable can store and its size. Examples int , char , float, double etc

• Identifier is variable name , such as following line declares Variable a of type int

Int a;

Data Types:

1	They are arithmetic types and are further classified into: (a) integer types and (b) floating-point types.
2	Enumerated types They are again arithmetic types and they are used to define variables that can only assign certain discrete integer values throughout the program.
3	The type void The type specifier void indicates that no value is available.
4	Derived types They include (a) Pointer types, (b) Array types, (c) Structure types, (d) Union types and (e) Function types.

Format Specifies :

• Format Specifiers determines the type of data which is to be entered or displayed, they are used in two places, Every data type in C has a format specifiers. Such as int has %d and %i, float has %f, char has %c and so on.

• 1) In taking Input

• 2) In displaying Output

Format Specifier	Description
%d or %i	Signed decimal integer
%o or %O	Unsigned octal
%x or %X	Unsigned hexadecimal integer
%f, or %F	Floating Point numbers
%e or %E	Scientific Notation
%g or %G	Shortest representation: %e or %f
%c	Character
%s	String
%p	Pointer Address
%%	%
l,h	long or short prefix for: d, i, u, o, x, X

Escape Sequence Characters in C

Escape sequence	Description
\'	single quote
\"	double quote
\?	question mark
\\	backslash
\a	audible bell
\b	backspace
\f	form feed - new page
\n	line feed - new line
\r	carriage return
\t	horizontal tab
\v	vertical tab
\nnn	arbitrary octal value
\xnn	arbitrary hexadecimal value
\unnnn	universal character name (arbitrary Unicode value); may result in several characters
\Unnnnnnnn	universal character name (arbitrary Unicode value); may result in several characters