Programming In QuickBASIC

3.2 Variables, Input And Output

3.2.1 Variable Names

Input and output data needs to be stored within the computer's memory.

Data is stored at a certain memory address. This box diagram represents an area of memory.

Variable names mean that the programmer does not have to remember what data is stored in which memory address.

In QuickBASIC names must not:

• exceed 40 characters in length.
• start with a digit.
• contain some certain non-alphanumeric characters.
• be distinguised from each other by variations in case.
• be a keyword.

3.2.2 Variable Types

Variables don't just come in one form.

There are:

Integers (2 bytes)

Any whole number from -32,768 to 32,767.

This is expressed as: variable_name%
or defined using the statement: DIM variable_name AS INTEGER

Long Integers (4 bytes)

Any whole number from -2,147,483,648 to 2,147,483,647.

This is expressed as: variable_name&
or defined using the statement: DIM variable_name AS LONG

Single Precision Floating Point Number (4 bytes)

Any real number with seven significant figures from -3.4×10³⁸ to 3.4×10³⁸.

This is expressed as: variable_name!
or defined using the statement: DIM variable_name AS SINGLE

Double Precision Floating Point Number (8 bytes)

Any real number with 15 significant figuresfrom -1.7×10³⁰⁸ to 1.7×10³⁰⁸.

This is expressed as: variable_name#
or defined using the statement: DIM variable_name AS DOUBLE

String

Any sequence of letters, symbols and numbers up to 32,767 characters in length.

This is expressed as: variable_name$
or defined using the statement: DIM variable_name AS STRING (length)

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