A program that always displays the same message can get a bit boring. Most programs get some information, do some calculations, then display the results of the calculations.
Information is stored in memory as variables. Variables can vary, or change. Before a variable can be used, it must be declared. To declare a variable, first decide what type of information you want to store:
- Whole numbers, number with no decimal places are called integers.
- Numbers with decimal places are called double.
- Single letters such as ‘Y’ or ‘N’ are characters.
- A variable that can only have the values true and false is boolean.
- Words, such as "Hello", or a person's name are Strings. Strings are somewhat more complicated because they require an array of memory locations. Strings are discussed in another chapter.