A method of loading a system program for apparatuses (SYS1, SYS2) that execute predetermined processing controlled by a system program that has been loaded into a memory. According to this loading method, the system program is divided into a plurality of modules (M1 to M4) which are stored on a floppy disc (FLOP); data (CD) are set in advance in ROMs (LROM1, LROM2) so that the capacities of memories (MM1, MM2), to which the system program wil be transferred and stored, are confirmed; the memory capacities of the apparatuses (SYS1, SYS2) are confirmed with reference to data (CD) at the time when the system program is being loaded such that a predetermined module is loaded onto the memories (MM1, MM2) based upon the memory capacity; the module (M4) that has not been loaded is then stored as a relocatable module in the memory (MM1) to substitute for an unnecessary module as required, and an execution control table (LAT) is prepared to control the memory position in the memory (MM1) of said relocatable module. When a relocatable module is to be referred to, the memory position is found by using the execution control table and the relocatable module is referred to.