PURPOSE: To generate a program so as to facilitate the manegement and maintenance of a program source and also to provide an effective program load means by word unit at the time transferring a load object for processing change-over.

CONSTITUTION: A first load object file and a second load object file which are generated from the program source where a whole application processing is described are adopted as an input so as to compare data by word unit between the files. An object difference means 31 which picks-up the load destination address and word data of the second load object file concerning the word with data difference so as to generate a stored difference object file and a data transfer means 32 which transfers load object data to the program memory of a processor 4 by word unit are provided so that the down load of object data adding the difference object is executed.