Remote-processing BASIC for the CX-10 Modbus Manual de usuario descargar pdf (Pagina 28)

BASIC PROGRAMMING GUIDE

2-19

FOR-TO-STEP-NEXT

Syntax: FOR

variable

initial index expr

index limit expr

[STEP

step expr

]

program statements

NEXT [

variable

]

Where:

variable

= any valid variable symbol

initial index expr

= starting value assigned to

variable

index limit expr

= ending value of

variable

step expr

= optional increment or decrement to

variable

when repeating a loop

Function: Looping structure useful for executing a sequence of instructions a number of times.

Mode: Run, command

Use: FOR A=0 to 4000 STEP 200 : AOT 0,A : NEXT

DESCRIPTION

The FOR-TO-STEP-NEXT instruction is a loop structure common to many high level languages. It is used to

perform

program statements

a number of times.

variable

is a loop counter initialized to

initial index expr

at the start of the loop. A number of

program

statements

are executed until NEXT is encountered. At this point the value of

step expr

is added to the value

variable

. The resulting new

variable

value is compared to the value of

index limit expr

. If the new value

variable

value is less than or equal to the value of

index limit expr

, all

program statements

are executed

again, and the test is repeated.

program statements

are always executed at least once. If

step expr

is larger than

index limit expr

, the loop

executes only once.

STEP is optional. When omitted, it defaults to 1. The value of

step expr

may be positive or negative.

FOR-NEXT loops may be inside other FOR-NEXT loops.

variable

following NEXT is optional.

There are two ways to break out of a for next loop and still maintain the control stack. The first is to execute

a CLEAR S command. This command also clears any subroutine return locations and DO-WHILE, DO-

UNTIL loops. Another is to set

variable

to a high value within

program statements.

When a program

continuously breaks out of a FOR-NEXT loop and re-declares a new loop, a C-Stack error is eventually

returned.

DO-UNTIL, DO-WHILE

ERROR

C-STACK NEXT without a corresponding FOR. This error can also appear if a number of FOR-NEXT

loops were set up but were illegally branched out of or re-declared.

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