Description

 

Declare and dimension variable and/or arrays.

 

Syntax

 

DIM VarName[(subscripts)] AS VarType [AT Address] [ {VALUE | = | VALUE =} InitialValue ]

DIM VarName[(subscripts)], VarName[(subscripts)] AS VarType [AT Address] [ {VALUE | = | VALUE =} InitialValue ]

DIM VarName[(subscripts)] AS VarType [ {VALUE | =} InitialValue ][, VarName[(subscripts)] AS VarType [AT Address] [ {VALUE | = | VALUE =} InitialValue ]

 

For fixed-len strings use the following syntax:

DIM VarName[(subscripts)] AS {STRING | ASCIIZ]} * Size [ {VALUE | = | VALUE =} InitialValue ]

 

For absolute variables or pointers use the following syntax:

DIM VarName[(subscripts)] AS VarType [AT Address | PTR] ...

DIM VarName[(subscripts)], VarName[(subscripts)] AS VarType [AT Address | PTR] ...

 

 

Returns

 

None

 

Parameters

 

Remarks

 

DIM keyword can be substituted with LOCAL or GLOBAL or STATIC or CONST.

 

 

 

AT address | PTR
This notation is also called Absolute location or addressing.
When a variable is created thinBasic sets each element of a numeric variable/array to zero, and sets each element of regular string variable/arrays to a null string (length zero).  However, when an absolute location is specified (at a specific location in memory using the AT address syntax), thinBasic does not initialize the memory occupied by the variable/array.  Further, when an absolute variable/array is erased, the memory is not released either.  This provides a powerful mechanism to create overlay structures in memory.
 
The most common use of an absolute variable/array is when manipulating variable/arrays generated by external DLL. This involves obtaining a pointer to the variable/array, the element size, and the number of elements.  With this information, an absolute variable/array can be dimensioned in thinBasic and the variable/array memory manipulated directly.  Another common use involves using a large dynamic or fixed-length string memory block, overlaid with an absolute numeric array.
 
Care must be exercised when using absolute variable/arrays, since the contents of an absolute array can only be valid for the scope of the memory the array references.  If an absolute variable/array references memory that is LOCAL to the sub/function, the variable/array contents become invalidated if the target memory block is released.

 

Restrictions

 

See also

 

ReDim

 

Examples

 

'---Some variables

Dim MyVar      As Number Value Timer

Dim MyStr      As String Value App_Path

Dim CountItems As Long   Value -1

 

Dim MyAsciiz As ASCIIZ * 256

Dim MyFixedLenString As STRING * 1024 VALUE "This is a big buffer string"

 

'---Other possible declaration ways

DIM a AS LONG

DIM a, b, c, d AS LONG

DIM a, b, c, d AS LONG = 123

DIM a AS LONG, b AS STRING, c AS EXT

DIM a AS LONG = 123456, b AS STRING = "ABC", c AS EXT = 1234.567

 

 

'---Arrays

Dim MaxItems As Long Value 10000

Dim MyArray(MaxItems) As String

Dim MyArray2(MaxItems) As String Value "Whatever string"

 

 

 

'---Undimensioned array redimensioned later

Dim MyUndimensionedArray() As String

'...

ReDim MyUndimensionedArray(MaxItems)