For those of you who may be new to amateur radio, (and for those who are not-so-new,) you may have found an occasion when you have heard something which is known as a Q code in ham radio. Q codes are abbreviations which were developed for common questions and responses that often accompany long-distance communications. These were historically used in Morse code to aid in telegraph transmissions during early 20th century. Because of the convenience of abbreviating frequent questions and answers, Q codes remain in use today, particularly in the HF bands. There are many Q codes out there which one may hear at one time or another. For your information, Q codes which begin with QAA-QNZ are generally reserved for aviation, and codes which begin with QOA-QQZ are for maritime purposes. This leaves the prefixes of QRA-QUZ for the use in radio, but as you can see below, there are a few exceptions. (The prefixes of QVA-QZZ are currently not assigned to any communication service.)
As for the codes used in amateur radio, a few are heard often, some are less common, and some are, for all practical purposes, obsolete. A list of all the codes may be difficult even for an experienced ham to remember. So if you ever found yourself wondering what in the world a particular Q code means, here are some Q code cheat-sheets you may print out for your personal use. You should know that by no means are the lists found here exhaustive. These are just some of the more common ones. If you think one (or more) codes not listed should be added here, please mention it in the comments below as I believe we could all benefit from it.