Abstract An investigation for the system initialization command file of ALPHA MICKO computer is described. Methods for reducing the size of the operating system have been studied. Some problems of the original file are pointed out and improvements have been made. The file improved contains five terminals and five jobs while the size of the operating system is less than 16 K bytes. Two methods are presented to avoid the abnormal running of the computer caused by users using the MEMORY 0 command simultaneously. A sample of the new file and its experimental result are given. The maximum number of terminals and jobs is also evaluated in view of actual effect.