Values

New programmers spend a lot of time thinking about what their programs must do. Mature programmers spend time designing a model for the data their programs must understand.

Variables allow us to manipulate data in the abstract. The values held in variables make programs concrete and useful. These values can be a name and an address, the distance between our office and a golf course on the moon, or the sum of the masses of the cookies we’ve eaten. Within our program, the rules regarding that data format are often strict.

Effective programs need practical (simple, fast, efficient, and easy) ways to represent their data.