variables and constants:

VARIABLES: A variable is an identifier that denotes a storage location used to store a data value. Unlike constants, a variable may take different values in different times during the execution of the program. A variable name can be chosen by the programmer in a meaningful way so as to reflect what it represents in the program. Some examples of variable names are:

1. average

2. height

3. total_height

4. classAverage

A variable names may consist of alphabets, digits, the underscore(_) and dollar characters, subject to the following conditions:

1. They must not begin with a digit.

2. Uppercase and lowercase are distinct. This means that the variable Total is not the same as total or TOTAL.

3. It should not be a keyword.

4. White space is not allowed.

5. Variable names can be of any length.

CONSTANTS: Constants are values which can never be changed. Constants can be directly used in expressions or they are assigned to variables.

o Integer constants: An integer type of variables can hold integer constants. There are three types of integers, namely, decimal, octal and hexadecimal integers.

Ex: int x=30

o Real (Float) constants: A real variable can hold float constants. They are whole numbers followed by a decimal point and fractional part. They may be expressed in scientific (exponential) notation.

Ex: float pi=3.14, x=0.64e4

o Char constants: A character variable can hold only one character. Character constant must be enclosed in single quotes.

Ex: char ch= ‘Q’

o String constants: String constant is a character array that can hold string values. Strings must be enclosed in double quotes.

Ex: String s= “kiran”, s1=”1234”;

o Boolean (logical) constants: Boolean constants are true and false. Unlike java, languages like C, C++ use integers to represent true or false.

Ex: boolean x=true

o Backslash Character Constants: These are used in output for formatting. All of these are similar to the ones which are available in C language. The constants and their meanings are listed below.

CONSTANT	MEANING
\b	backspace
\f	form feed
\n	new line
\r	carriage return
\t	horizontal tab
\’	single quote
\”	double quote
\\	backslash