Variables
A variable is a place to store a piece of information.
Variables are those quantities whose value vary during the execution of the program.
Variable name is a name given to memory cells location of a computer where data is stored.
Declaring a Variable :
You have to tell the computer that you are going to stora a number in a variable before you
can actually do it. This is called variable declaring.
To declare a variable, you need to know what kind of information it will store like will it store
an integer number, floating number or a text-string, or something else.
This will be done by using 'DATA TYPES'.
Syntax :
Data type variable-name
Example :
int x, float y
Rules of naming variables :
Variable name must begin with a letter.
Keywords are not allowed to use as a variable name.
White space is not allowed.
Only underscore, special symbol is allowed between two characters.
Variable names are case sensitive, hence x and X are different.
These can't have special characters.
The length of indentifier may be upto 31 characters but only only the first 8 characters are significant by compiler.
Constants :
Constants are those quantities whose value does not vary during the execution of the program
that is, value is fixed.
C has two types of constants :
1. Numeric constants
2. Non numeric constant
Numeric constants :
Thses have numeric value having combination of sequence of digits i.e. from 0-9 as
alone digit or combination of 0-9 with or without decimal point having positive or
negative sign.
These are further sub-divided into two categories :
(a) Integer Numeric constant
(b) Real or float Numeric constant
Integer Numeric constant :
These have integer data combination of 0-9 without any decimal point.
It can be positive or negative.
Use of blank space and comma is not allowed between integer constants.
Example:
420,-34 etc.
Real or Float Numeric constant :
It must have at least one digit.
It must have a decimal point which may be positive or negative.
Use of blank space and comma is not allowed between real constants.
Example:
20.4,52.54 etc.
Character constants :
These have either a single character or a group of characters or a character with backslash
used for special pupose.
These are of following types :
1. Single character constant
2. String character constant
3. Backslash character constant
Single character constant :
It is a single alphabet or a digit or a special symbol enclosed in a single quote.
Maximum length of a character constant is 1.
Example:
'A','R','$' etc.
String character constant :
It is collection of characters enclosed in double quotes.
It may contain letters, digits, special characters and blank space.
Example:
"bestprogrammingtutorials"
Backslash character constant or Escape sequence :
These are discussed in the topic.
