Abbreviating and capitalizing are treated together because sometimes words are both abbreviated and capitalized. Capital letters emphasize the abbreviation, and periods after capitalization are fast disappearing, but there are exceptions. Abbreviation and capitalization vary widely from agency to agency, state to state, and service to service. Although many agencies have a prohibition in their report-writing manuals against using abbreviations, most people do use abbreviations. Ironically, although many agencies and departments have a prohibition against using abbreviations, they produce forms that do not have room for anything more than abbreviations. Numbers and codes may be used with the supposition that they are understood only by a restricted number of individuals. The codes used in radio communications and over public announcement systems by various agencies are a form of abbreviation that sometimes appears in criminal justice reports. A few abbreviations are so well known and so unique that it would seem ridiculous to write them out.