Q.Give an example for each valid variable and invalid variable.

A variable is a named location in memory whose value can change during execution. Before a variable is used it must be declared, which tells the compiler its name and the data type of the value it will hold.

The name given to a variable is an identifier. The rules for forming an identifier (or variable) name are: it may contain only letters, digits and the underscore _; it must begin with a letter or underscore (not a digit); it must not be a keyword; and it must contain no spaces or special symbols. Thus area, sum_1 and _count are valid, while 2x, net pay and int are invalid. …