PURPOSE: To reduce the size of a load module at the time of preservation to effectively use an auxilairy storage device and to shroten starting time at the time of executing the load module by compressing same continuous data of the load module.

CONSTITUTION: A load module execution system is provided with a main storage device 6, the auxiliary storage device 4, a load module compression mechanism 1 compressing the load module in an operating system, a load, mechanism 2 transferring the load module on the main storage device 6 and a load module expansion mechanism 3 expanding the load module. The load module 7 of the execution from is temporarily preserved in the auxiliary storage device 4. When the load module of the execution form is stored in the auxiliary storage device 5, the load module compression mechanism 1 compresses the data structure of the load module.