01
Boolean Values TRUE and FALSE
What TRUE and FALSE mean in PLC programs and how they relate to real signals.
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Boolean logic
Logic values, operations, and truth tables
This track explains TRUE/FALSE conditions, why AND needs two active inputs, how OR differs from XOR, and how to move an expression into an FBD diagram.
What you learn
TRUE and FALSE describe condition state: button pressed, sensor active, permissive available.
AND, OR, NOT, and XOR combine simple conditions into expressions.
In FBD each operation becomes a block and connections show signal flow.
A truth table checks every input combination before running the diagram.
Track topics
TRUE / FALSEANDORNOTXORtruth tableslogic expressionspractical tasks
Related lessons
Logic lessons
02
The AND Logic Operation
AND activates an output only when all required permissives are satisfied together.
Read lesson03
The OR Logic Operation
OR combines commands or conditions when one active signal is enough.
Read lesson04
The NOT Logic Operation
NOT inverts signals to express inhibits, faults, and active-low conditions.
Read lesson05
Truth Tables
Check logic diagrams against every combination of input signals.
Read lesson06
De Morgan's Laws in Logic Diagrams
Transform NOT, AND, and OR expressions, verify equivalence with a truth table, and apply De Morgan's laws in FBD.
Read lesson07
Binary Half Adder
Learn how XOR and AND add two one-bit binary numbers and produce the SUM and CARRY signals.
Read lessonPractice
Basic logic examples
Open an example, toggle inputs, and compare the output with the truth table.
Lamp from one button
A direct input-to-output connection shows the basic meaning of TRUE/FALSE.
Open exampleLamp from two buttons with AND
The lamp turns on only when both buttons are active.
Open exampleLamp from two conditions with OR
One active condition is enough to turn on the output.
Open exampleA AND NOT B
Permissive A works only while blocking condition B is not active.
Open exampleXOR as different states
The output is TRUE when two inputs are in different states.
Open example