This is study of two high-performance microprocessor architectures: the Intel 8086 family and the Motorola 68000 family. Comparatively discussing the 16-bit microprocessors, 8086 and 68000 with the 32-bit microprocessors, 80386 and 68020, the text uses a systems-oriented approach to provide coverage of the microprocessor, its architecture, assembly language programming and hardware interfacing techniques. The work defines software architecture - register model, memory address space, data organization, user and supervisor stacks and operand addressing modes. It also shows the practical circuits for implementing hardware interfaces in a microcomputer system, and provides an introduction to instruction sets and their use in writing practical programs, and VLSI I/O peripheral ICs.