Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario descargar pdf (Pagina 56)

Operating Functions

Chapter 5

5–19

Mode: COMMAND AND/OR RUN

Type: Assignment

DIM reserves storage for matrices. The storage area is first assumed to

be zero. Matrices in the BASIC Module may have only one

dimension and the size of the dimensioned array may not exceed 254

elements. Once a variable is dimensioned in a program it may not be

re-dimensioned. An attempt to re-dimension an array causes an

ARRAY SIZE ERROR. If an arrayed variable is used that is not

dimensioned by the DIM statement, BASIC assigns a default value of

10 to the array size. All arrays are set equal to zero when the RUN

command, NEW command or the CLEAR statement is executed. The

number of bytes allocated for an array is 6 times the array size plus 1.

The array A(100) requires 606 bytes of storage. Memory size usually

limits the size of a dimensioned array.

Variations: More than one variable can be dimensioned by a single

DIM statement.

Example:

u10 DIM A(25), B(15), A1(20)

Example: Default error on attempt to re-dimension array

u10 A(5)10 –BASIC ASSIGNS DEFAULT OF 10 TO ARRAY SIZE HERE

u20 DIM A(5) –ARRAY CANNOT BE RE–DIMENSIONED

uRUN

ERROR: ARRAY SIZE – IN LINE 20

20 DIM A(5)

-X

Mode: RUN

Type: CONTROL

The DO – UNTIL [rel expr] instruction provides a means of “loop

control” within a module program. All statements between the DO

and the UNTIL [rel expr] are executed until the relational expression

following the UNTIL statement is TRUE. You may nest DO – UNTIL

loops.

5.4.7

Statement: DIM

5.4.8

Statements: DO – UNTIL

[rel expr]

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Rockwell-automation 1771-DB Basic Module User Manual - Series A Manual de usuario Pagina 56