Mach: a system software kernel

for a 16-bit uniprocessor. Under the weight of changing Abstract needs and technology, Unix has been modified to provide a staggering number of different mechanisms for managing obThe Mach operating system can be used as a system software kernel which can support a variety of operating jects and resources. In addition to pipes, Unix versions now system environments. Key elements of the Mach design support facilities such as System V streams, 4.2BSD sockets, which allow it to efficiently support system software include pty’s, various forms of semaphores, shared memory and a integrated virtual memory management and interprocess commind-boggling array of ioctl operations on special files and munication, multiple threads of control within one address devices. The result has been scores of additional system calls space, support for transparent system trap callout and an object programming facility integrated with the Mach IPC and options with less than uniform access to different mechanisms. Mach is currently available both from CMU resources within a single Unix system and within a network of and commercially on a wide range of uniprocessor and mulUnix machines. tiprocessor hardware. The Mach operating system kernel developed at Carnegie Mellon University [1] was designed to operate on both