Rockwell Automation 1771-DB BASIC MODULE - Manual (Page 159)

Chapter
Statements 11
11 -7
Use the DIM statement to reserve storage for arrays. The storage area is
first assumed to be zero. Arrays in the BASIC module may have only one
dimension and the size of the dimensioned array may not exceed 254
elements.
Once you dimension a variable in a program you may not re-dimension it.
An attempt to re-dimension an array causes an array size error and the
module enters the Command mode.
If you use an array variable that you did not dimension by a DIM
statement, BASIC assigns a default value of 10 to the array size.
All arrays are set equal to zero when you execute the RUN command (page
10 -19), NEW command (page 10 -10) or the CLEAR statement (page
11 -2).
The number of bytes allocated for an array is six times the array size plus
one (6
∗
(array size + 1)). For example, the array A (100) requires 606 (6
* (100+1)) bytes of storage. Memory size usually limits the size of a
dimensioned array.
Important: If using strings you must define them in your program with
the STRING statement (page 11 -37) before you define arrays with the
DIM statement.
Syntax
DIM
Example
>1 REM EXAMPLE PROGRAM
>10 DIM A(25), C(15), A1(20)
Error on attempt to re-dimension array:
>1 REM EXAMPLE PROGRAM
>10 A(5) = 10 :REM BASIC ASSIGNS DEFAULT OF 10 TO ARRAY A
>20 DIM A(5) : REM ARRAY RE–DIMENSION ERROR
READY
>RUN
ERROR: ARRAY SIZE – IN LINE 20
20 DIM A(5) : REM ARRAY RE–DIMENSION ERROR
–––––––––––––––X
READY
>
DIM