Variables
A
variable
is an identifier that is declared in a method and that stands for a
value within that method. Its value is allowed to change within the
method. Each variable is of a particular type, and that type is
indicated in the declaration of the variable. For example, this line
declares a variable named i
whose type is Integer:
Dim i As Integer
The keyword Dim
indicates a variable declaration.
Dim is short for dimension
and dates back to the original days of the BASIC programming language
in the late 1960s. In that language, variables were not declared;
they were just used where needed (except for arrays). Because of how
arrays were laid out in memory, the BASIC language interpreter had to
be told of the dimensions of an array before the array was used. This
was the purpose of the Dim
statement. In later
years, when declaration of all variables was agreed upon to be a
good thing, the use of the
Dim
statement was broadened to include all
variable declarations.
Variable identifiers may be suffixed with type characters that serve to indicate the variable’s type. For example, this line declares a variable of type Integer:
Dim x%
The effect is precisely the same as for this declaration:
Dim x As Integer
The set of type characters is shown in Table 2-4; note that not all data types have a type character.
Table 2-4. Type characters
Data type |
Type character |
Example |
---|---|---|
Decimal |
@ |
|
Double |
# |
|
Integer |
% |
|
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