1. A method of generating a symbol table for a programmable logic controller which executes high-level language program and controls devices, the method comprising: reading a source code of the high-level language program and an association table wherein the association table defines a relationship between device names that are not supported by the high-level language program and variable names for the respective devices used in the high-level language program; compiling the source code of the high-level language program into assembly code to determine a physical address in a memory of the programmable logic controller for each of the variable names; generating the symbol table based on the association table and the physical address for each of the variable names determined by the compiling, the symbol table defining the determined physical address for each of the variable names and the names of the target device; and storing the symbol table in a memory of the programmable logic controller.