A revised and expanded (2013) introduction to the IBM mainframe assembly language and architecture including addressing models, basic and extended instruction formats, operand addressing, the Program Status Word, subroutine linkage, looping, input output, character & bit manipulation, and the decimal (BCD) programming. The book includes more than 40 pages of comprehensive programming examples. Designed to be used in conjunction with the Window's based open source, z390 mainframe emulator. Assumes no prior knowledge of assembly language programming.About the author: the author is professor emeritus of computer science at the University of Northern Iowa in Cedar Falls, Iowa where he taught IBM assembly language for over twenty years.