Program Variables

One of the most powerful aspects of computer programming is the ability to process variable data to achieve a result. Regardless of the complexity of a process, when data is unknown or varies, you substitute a symbol for the data. This is much like substituting x and y in an algebraic equation.

x = y + 29

The symbol, when its value can vary, is called a variable. A group of symbols or numbers that must be calculated to be resolved is called an expression.