The Norton Guides were a product family sold by Peter Norton Computing. The guides were written in 1985 by Warren Woodford for the x86 Assembly Language, C, BASIC, and Forth languages ( wikipedia ). The Assembly Language Norton Guide is a complete reference document about x86 assembly language, where you'll find the instruction set ( processor and coprocessor ), directives and operators, reserved words, interrupts and functions ( ROM BIOS, DOS ), low memory usage, PSP structure and many other topics. It acts like a help when you forget any commands or "magic numbers".