It is usual for people to associate a name or phrase with a piece of information. Note that it is good programming practice to use variable names that are reminiscent of the information being referred to. It is important for a computer to identify the type of data it has stored. Integers are more accurate for discrete values and are processed fastest, but reals are necessary for many calculations.
Complex numbers are necessary for some scientific applications.
As well as numeric data, Fortran programs often require other types of data. Finally, It is possible not to use a variable to represent data but to use the value explicitly. For example, instead of using pi , a programmer might choose to write 3.14159. Such values are known as literal constants. In a Fortran program, variable names must correspond to a naming convention.