Exploring the IF statement
The most rudimentary control statement that all PLC developers will need to master is the IF statement. As the name suggests, this command will run a block of code if, and only if, a certain logical expression evaluates to True. Much as with logical expressions, the IF statement must be mastered, especially for PLC programming.
IF statement syntax
The IEC 61131-3 syntax for the IF statement is somewhat like the VAR declaration block. The basic structure for the IF statement is as follows:
IF <expression> THEN //code to run END_IF
For this structure, the expression is a logical expression such as determining if two values are equal. In between IF and END_IF is what’s called the body. The body is the code that will run when the expression is True. Technically, you can have as much code in the body as you want, but it is advisable to keep the body as short as possible. To really understand the IF statement...
