Which programming language is used to program a PLC and is described as ladder-like with rails and rungs?

Which programming language is used to program a PLC and is described as ladder-like with rails and rungs?

• A. Ladder Logic
• B. Structured Text
• C. Function Block Diagram
• D. Instruction List

Answer: (A)

The concept being tested is how PLC programming languages map to the way control circuits are drawn. The description of a ladder-like structure with rails and rungs points to Ladder Logic. In Ladder Logic, you see a vertical pair of rails representing power, and horizontal rungs that contain symbols for inputs (like normally open or normally closed contacts) and outputs (coils). When the conditions on a rung are satisfied, the corresponding output coil is energized, effectively closing a circuit to drive machinery. This graphical style mirrors traditional relay-based control diagrams, which makes it intuitive for technicians and easy to translate from hard-wired designs to software. Other languages in IEC 61131-3 are not drawn as ladders: Structured Text is a high-level, text-based language similar to Pascal or C; Function Block Diagram uses blocks and connections to represent data flow between functions; Instruction List is a low-level, assembly-like textual language. Their forms don’t resemble the ladder with rails and rungs, which is why Ladder Logic is the one described.

The concept being tested is how PLC programming languages map to the way control circuits are drawn. The description of a ladder-like structure with rails and rungs points to Ladder Logic. In Ladder Logic, you see a vertical pair of rails representing power, and horizontal rungs that contain symbols for inputs (like normally open or normally closed contacts) and outputs (coils). When the conditions on a rung are satisfied, the corresponding output coil is energized, effectively closing a circuit to drive machinery. This graphical style mirrors traditional relay-based control diagrams, which makes it intuitive for technicians and easy to translate from hard-wired designs to software.

Other languages in IEC 61131-3 are not drawn as ladders: Structured Text is a high-level, text-based language similar to Pascal or C; Function Block Diagram uses blocks and connections to represent data flow between functions; Instruction List is a low-level, assembly-like textual language. Their forms don’t resemble the ladder with rails and rungs, which is why Ladder Logic is the one described.