Norton Guides were a product family sold by Peter Norton Computing. The guides were written in 1985 by for the x86 Assembly Language, C, BASIC, and Forth languages and made available to DOS users via a Terminate and Stay Resident (TSR) program that integrated with programming language editors on IBM PC type computers. Norton Guides were compiled from ASCII source files with a tool called NGC. Morten Elling wrote an alternative guides compiler NGX in 1994 or earlier. A utility to view Norton Guides .ng files is found at http://www.davep.org/norton-guides/