Pascal Tutorial 1D - Variables and Data Types

1D - Variables and Data Types

Variables are similar to constants, but their values can be changed as the program runs. Unlike in BASIC and other loosely-typed languages, variables must be declared in Pascal before they can be used:

     var
        IdentifierList1 : DataType1;
        IdentifierList2 : DataType2;
        IdentifierList3 : DataType3;
        ...

IdentifierList is a series of identifiers, separated by commas (,). All identifiers in the list are declared as being of the same data type.

The main data types in Pascal are:

     integer
     real
     char
     Boolean

Note that although constants may be strings, there is no built-in type called string except in some specialized implementations (such as Turbo Pascal).

More information on Pascal data types:

integer data type can contain integers from -32768 to 32767.
The real data type has a positive range from 3.4x10^-38 to 3.4x10³⁸. Real values can be written in either fixed-point notation or in scientific notation, with the character E separating the mantissa from the exponent. Thus,
452.13 is the same as 4.5213e2
The char data type holds characters. Be sure to enclose them in single quotes, or apostrophes:
'a' 'B' '+'
This data type can also hold system characters, such as the null character (ordinal value of 0) and the false-space character (ordinal value of 255).
The Boolean data type can have only two values:
TRUE and FALSE

An example of declaring several variables is:

     var
        age, year, grade : integer;
        circumference : real;
        LetterGrade : char;
        DidYouFail : Boolean;