Donald Lewine has been writing computer programs for fun and profit since 1960. He has been teaching computer science in the State-of-the-Art (evening) program at Northeastern University for the past eight years. He has taught courses on Assembler, VAX/VMS, PASCAL, C and UNIX. This book was written and tested over the last two years at Northeastern University. Mr. Lewine spent 13 years with the Digital Equipment Corporation developing operating systems and central processing units. He was Technical Director for the MicroVAX Program when he left. For the past seven years, Mr. Lewine has been with Data General Corporation, currently as Director of Engineering. In this role he has been developing the AViiON family of open systems. He is a founder and a member of the Board of Directors of 88open, a member of the Board of Directors of UNIX International, and Data General's representative to the Open Software Foundation.