a CRT screen, and was used as an interactive online editor. Later versions of TECO were capable of driving full-screen mode on various DEC RS-232 video terminals such as the VT52 or VT100. TECO was available for several operating systems and computers, including the PDP-1 computer, the PDP-8 (under OS/8), the Incompatible Timesharing System (ITS) on the PDP-6 and PDP-10, and TOPS-10 and TOPS-20 on the PDP-10. A version of TECO was provided with all DEC operating systems; the version available for RT11 was able to drive the GT40 graphics display while the version available for RSTS/E was implemented as a multi-user run-time system and could be used as the user's complete operating environment; the user never actually had to exit TECO. The VTEDIT (Video Terminal Editor) TECO macro was commonly used on RSTS/E and VAX systems with terminals capable of direct-cursor control (e.g. VT52 and VT100) to provide a full-screen visual editor similar in function to the contemporaneously developed Emacs. TECO continues to be included in OpenVMS by VSI, and is invoked with the EDIT/TECO command. A descendant of the version DEC distributed for the PDP-10 is still available on the Internet, along with several partial implementations for the MS-DOS/Microsoft Windows environment. History TECO was originally developed at MIT in around 1963 by Daniel L. Murphy for use on two PDP-1 computers, belonging to different departments, both housed in MIT's Building 26. On these machines, the normal development process involved the use of a Friden Flexowriter to prepare source code offline on a continuous strip of punched paper tape. Programmers of the big IBM mainframes customarily punched their source code on cards, using key punches which printed human-readable dot-matrix characters along the top of every card at the same time as they punched each machine-readable character. Thus IBM programmers could read, insert, delete, and move lines of code by physically manipulating the cards in the deck. Punched paper tape offered no such amenities, leading to the development of online editing. An early editor for the PDP-1 was named "Expensive Typewriter". Written by Stephen D. Piner, it was the most rudimentary imaginable line-oriented editor, lacking even search-and-replace capabilities. Its name was chosen as a wry poke at an earlier, rather bloated, editor called "Colossal Typewriter". Even in those days, online editing could save time in the debugging cycle. Another program written by the PDP-1 hackers was Expensive Desk Calculator, in