WHILE Statement

The WHILE statement is an iteration structure for a group of Structured Text (ST) statements. The "continue" condition is evaluated BEFORE any iteration
WHILE Statement
Name
WHILE ... DO ... END_WHILE
Syntax
WHILE <Boolean_expression> DO
<statement> ;
<statement> ;
...
END_WHILE ;
IMPORTANT: Since the virtual machine is a synchronous system, input variables are not refreshed during WHILE iterations. The change of state of an input variable cannot be used to describe the condition of a WHILE statement.
Example
(* ST program using WHILE statement *)

(* this program uses specific "C" functions to read characters *)

(* on a serial port *)

str := ''; (* empty string *)

nbchar := 0;

WHILE ((nbchar < 16) & ComIsReady ( )) DO

str := str + ComGetChar ( );

nbchar := nbchar + 1;

END_WHILE;
To insert a WHILE statement
  • From the
    Toolbox
    , drag the
    WHILE
     element into the language container.
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