PURPOSE: To curtail remarkably the number of steps for generating a program by registering in advance in a command a subroutine required for a program and a specified function.

CONSTITUTION: A command program is pre-compiled by referring to a command and user command development definition files 25, 26 by an operation language pre-compiler 29, become a FORTRAN source program and is dropped into a source program 31. In this process, a program implementor can fetch and utilize a list related to what kind of command table exists in the electronic computer system concerned, and how the command development definition is executed, by a command table 23, a command development definition list 24, and also an output 30 of message information. Also, error information and a message of the time when generating the program can be outputted to a programmer.