ISPSoft User Manual 10.1 Introduction of a Ladder Diagram A ladder diagram is one of the programming languages defined by IEC 61131-3, and is widely used to create a PLC program. A ladder diagram is a programming language that represents a program by a graphical diagram based on the circuit diagrams of relay logic hardware. A ladder diagram in ISPSoft is shown below. *. Please refer to DVP-PLC Application Manual ─ Programming for more information about ladder diagrams. 10.1.1 Editing Environment Select the Ladder Diagram (LD) option button in the Language section in the Create Program window. Please refer to section 5.4.1 for more information. 10-2