Table of Contents

DIM

PET VIC-20 C64 C16 Plus/4 C128 X16 M65

DIM is used for defining variables and arrays.

Syntax

DIM|STATIC [SHARED] [FAST] _
<variable name>[(<array dimensions>)] AS <type> [@<address>] _
[, <variable name>[(<array dimensions>)] AS <type> [@<address>] ... ] _
[SHARED] [FAST]

DIM is used to explicitly define variables and assign them a type. Since XC=BASIC is a statically typed programming language, all variables must be defined before they can be used. While some variables can be auto-defined by the compiler without the use of the DIM statement (known as “implicit definition”), the use of DIM ensures the variable is defined as the intended type.

  • The keyword is either DIM or STATIC. The latter is used for defining a static variable in dynamic subroutines and functions. Read more here
  • Array dimensions are specified in parenthesis. The maximum number of dimensions is 3 and the maximum length of one dimension is 32768.
  • The AS keyword is mandatory and the variable type must be defined. The type can be a numeric, string or user-defined type as well. If the variable is defined as string, the string length must be also given, for example DIM mystr$ AS STRING * 16
  • SHARED can be used to set the variable's visibility to shared, that means the variable is visible from within all code modules.
  • The FAST keyword instructs the compiler to reserve space for the variable on the zero page, if available. If no more zero page space is available, the keyword will be ignored with a warning.
  • If the @<address> is provided, the compiler will place the variable at the given address in memory. It can be either be:
    • a numeric literal between 0 and $FFFF (65535).
    • a constant
    • a label

Examples

' define single variables
DIM enemy_count AS INT
DIM score AS DECIMAL
DIM gravity AS FLOAT
DIM name$ AS STRING * 16

' define multiple variables in a single statement,
' all in the shared scope
DIM SHARED a AS INT, b AS WORD, c AS FLOAT

' dimension an array of 24 INT variables
DIM rockets(24) AS INT

' define a variable with explicit address
DIM my_var AS INT @ $C000

Additional Details

Note

Refer to the Variables page for more information on defining variables. Refer to the Data Types page for more information on variable types and their use.

See Also