Storing data in computer programs

Storing data in computer programs
For those new to computer programming, data and code go hand in hand. You cannot write a program of any real value without lines of code, or without data. A Word Processor program has logic that takes what the user types and stores it in data. It also uses data to control how it stores and formats what the user types and clicks.

Data is stored in the memory of the computer when the program runs (it can also be stored in a file, but that is another matter beyond the scope of this tutorial). Each memory 'slot' is identified by a name that the programmer chooses. For example LineTotal might be used to name a memory slot that holds the total number of lines in a Word Processor document.

The program can freely read from and write to this memory slot. This kind of data is called a Variable. It can contain data such as a number or text. Sometimes, we may have data that we do not want to change. For example, the maximum number of lines that the Word Processor can handle. When we give a name to such data, we also give it its permanent value. These are called constants.