Variables

A variables is a data name used to store a data value. Variable names are names given to location in the memory where different constants are stored. Unlike a constant which remains unchanged during the execution of a program, a variable can take different values at different times during execution.
A variable name is a combination of alphabets,digits or underscores. The first character however must be an alphabet. No commas, or blank are allowed while constructing variable. The variable name should not be keyword. Variables are case sensitive i.e. sum and SUM are two distinct variables.
Some valid variable names are:
Max_length age xyz avg a1 T1