Statements: gosub [ln num] – return – Rockwell Automation 1771-DB Basic Module User Manual - Series A User Manual

Page 60

Operating Functions

Chapter 5

5–23

Since B=0, C=10 and D=2,

the PRINT statement at line 20 executes

6 times. The values of “A” printed are 0, 2, 4, 6, 8 and 10. “A” represents
the name of

the index or loop counter. The value of “B” is the starting

value of the index. The value

of “C” is the limit value of the index and

the

value of “D” is the increment to the index. If the STEP statement

and the value “D” are omitted,

the increment value defaults to 1,

therefore, STEP is an optional statement.

The NEXT statement adds

the value of “D” to the index.

The index is then compared to the value of

“C”, the limit.

If the index is less than or equal to the limit, control

transfers

back to the statement after the FOR statement. Stepping

“backwards”

(FOR I= 100 TO 1 STEP–1) is permitted in the BASIC

Module. You may not

omit the index from the NEXT statement in the

module (The NEXT statement

is always followed by the appropriate

variable). You may nest FOR-NEXT loops up to 9 times.

Examples:

u10 FOR I=1 TO 4

u10 FOR I=O TO 8 STEP 2

u20 PRINT I,

u20 PRINT I

u30 NEXT I

u40 END

uRUN

1 2 3 4

0
2
4
6
8

READY

Mode: RUN
Type: CONTROL

GOSUB

The GO SUB [ln

num] statement causes the BASIC Module to

transfer

control of the program directly to the line number ([ln num])

following the GOSUB statement.

In addition, the GOSUB statement

saves the location

of the statement following GOSUB on the control

stack so that you can perform a RETURN statement to return

control to

the statement

following the most recently executed GO SUB

STATEMENT.

5.4.11
Statements: FOR – TO –
(STEP) – NEXT (continued)

5.4.12
Statements: GOSUB
[ln num] – RETURN