PS is an abbreviation for postscript. It is derived from the Latin postscriptum, which meaning "written after." A postscript is a thought that is added to letters (and occasionally other documents) after they have been completed. The term is now used generally for any additional writing that follows another document. In computer technology, a postscript is a type of portable document format file used by printers to record information about how pages are printed. Printer manufacturers can use this information to improve print quality and file compatibility with future versions of their products. The PostScript language was created by John Warnock, Tom Beddard, and Terry Licklider at Adobe Systems. It was released in January 1983 as a successor to their previous printer language, PCL, which had been introduced in 1980. Although PCL was designed to make it easy for users to create their own printing commands, it lacked many features that are now standard in word processing programs. By adding more sophisticated features to PostScript, such as vector graphics, text shadows, and optical-quality typography, Adobe was able to provide users with high-end capabilities that were not available from other companies at the time. Adobe's first commercial release of PostScript was called DisplayPostScript. It allowed printers to display pages on the screen instead of printing them.