Some important re formations and extentions that the authors made for MINIX operating system, a time-sharing、 multiuser、 multitask operating system developed by A. S. Tanenbaum in 1986 and used for teaching of operating system course, are described in details in this paper, including support for 3. 5” floppy disk, utilization of extended memory, and implementation of process swapping and spooling mechanisms.