1, sfc-seasonal function diagram This is a graphic language on top of other programming languages, which is used to compile SFC-Seauential control programs (such as manipulator control programs). 2. Ladder diagram, which is the most commonly used PLC programming language. Because it is very similar to relay circuit, intuitive and easy to understand, easy to be mastered by electrical personnel familiar with relay control, especially suitable for digital logic control. 3.STL-STatement List is a text programming language similar to microcomputer assembly language, which consists of several statements to form a program segment. Language tables are suitable for experienced programmers. 4.FBD- functional block diagram The functional block diagram uses graphic logic symbols similar to Boolean algebra to represent control logic, and some complex functions are represented by instruction boxes, which is suitable for programmers with digital circuit foundation. Functional block diagram uses a block diagram similar to AND gate or OR gate to represent the logical operation relationship. The left side of the block is the input variable of logical operation, and the right side is the output variable. The small circle at the input and output end represents NOT operation, and the blocks are connected by wires, and the signals are from left to right. 5. Structured TextStructured Text (ST) is a special high-level programming language created for IEC 61131-3 standard. The S7 SCL structured control language of STEP7 is similar to C language and Pascal language in programming structure, which is suitable for people who use high-level languages to program.