Code wheel

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Code wheel" – news · newspapers · books · scholar · JSTOR (September 2008) (Learn how and when to remove this message)

A code wheel is a type of copy protection used on older computer games, often those published in the late 1980s and early 1990s. It evolved from the original "manual protection" system in which the program would require the user to enter a specific word from the manual before the game would start up or continue beyond a certain point. This system was popular because it allowed the actual media to be backed up and replaced freely while retaining security, but with the increased availability of photocopiers, those wishing to distribute the games simply started copying their manuals as well to defeat the measure.

Although whole code wheels could not be directly photocopied, the component wheels could be disassembled and individually photocopied; these components could then be crafted together into a duplicate wheel. The contents of code wheels could also be copied onto paper and the user of an unlicensed copy could simply apply a mathematical formula to the presented challenges to calculate the correct response. Once a suitable formula was found, code wheels actually made the process of copying easier since the amount of information they could contain was low compared to a manual of potentially unlimited size. Thus, code wheels were rapidly phased out in favor of regular manual protection and protection based around color, as public access to color photocopying at the time was expensive and uncommon. This was itself made obsolete by a return to protection based on the game media itself, when CD-ROMs were introduced.