The book provides the detailed information necessary to write practical programs under Mach。 It shows applications writers and programmers how to create programs with multiple threads of control and make use of advanced interprocess communication mechanisms in a multi-processor environment。 In addition the book illustrates， with complete example programs， how to fully exploit the functionality Mach provides。 This book describes the differences between Mach and UNIX 4。3 BSD and OSF/1， two popular operating systems which share a common heritage with Mach。