IF-THEN-ELSIF-ELSE-END_IF statement

This section is about IF-THEN-ELSIF-ELSE-END-IF statement syntax and examples.
The ELSE and ELSIF statements are optional. If the ELSE statement is not written, no instruction is executed when the condition is FALSE.
You can use the ELSIF statement more than once. The ELSE statement, if used, must appear only once at the end of the "IF, ELSIF..." sequence.
Properties of IF-THEN-ELSIF-ELSE-END-IF statement
Item
Description
Name
IF ... THEN ... ELSIF ... THEN ... ELSE ... END_IF
Meaning
Executes one of several lists of structured text statements.
A selection is made according to the value of a Boolean expression.
Syntax
IF <Boolean_expression> THEN
    <statement> ;
    <statement> ;
    ...
ELSIF <Boolean_expression> THEN
    <statement> ;
    <statement> ;
    ...
ELSE
    <statement> ;
    <statement> ;
    ...
END_IF;

Example

(* ST program using IF statement *)

IF manual AND not (alarm) THEN
level := manual_level;
bx126 := bi12 OR bi45;
ELSIF over_mode THEN
level := max_level;
ELSE
level := (lv16 * 100) / scale;
END_IF;

(* IF structure without ELSE *)
If overflow THEN
alarm_level := true;
END_IF;
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