Plc

A PLC comprising:

• an I/O module to which an external device is connected;
• a CPU module for executing an execution program controlling the I/O module;
• a connector for electrically connecting the I/O module and the CPU module to each other;
• and
• a display device including a display screen,
• wherein the CPU module includes:
• a first storage unit which previously stores an intrinsic control program in which an operation program indicative of operation processing corresponding to the I/O module and an input/output information item indicative of the operation processing are packaged;
• a second storage unit which previously stores a function block representing the operation processing by a single symbol;
• a third storage unit which previously stores an equivalent input/output information item equivalently representing the input/output information item by a graphical language;
• an ID number acquisition unit which reads out ID number of the I/O module electrically connected to the connector;
• a program creation unit which calls one of the control programs corresponding to the read ID number and automatically creates the execution program from the called control program;
• and
• a main storage unit which stores the execution program created by the program creation unit, and
• wherein the display device includes a display unit which causes the execution program stored in the main storage unit to be displayed by using the function block and the equivalent input/output information item by referring to the second storage unit and the third storage unit.