a similar vein. The original stated purpose of TECO was to make more efficient use of the PDP-1. As envisioned in the manual, rather than performing editing "expensively" by sitting at a console, one would simply examine the faulty text and prepare a "correction tape" describing the editing operations to be performed on the text. One would efficiently feed the source tape and the correction tape into the PDP-1 via its high-speed (200 characters per second) reader. Running TECO, it immediately would punch an edited tape with its high-speed (60 characters per second) punch. One could then immediately proceed to load and run the assembler, with no time wasted in online editing. TECO's sophisticated searching operations were motivated by the fact that the offline Flexowriter printouts were not line-numbered. Editing locations therefore needed to be specified by context rather than by line number. The various looping and conditional constructs (which made TECO Turing-complete) were included in order to provide sufficient descriptive power for the correction tape. The terse syntax minimized the number of keystrokes needed to prepare the correction tape. The correction tape was a program, and required debugging just like any other program. The pitfalls of even the simplest global search-and-replace soon became evident. In practice, TECO editing was performed online just as it had been with Expensive Typewriter (although TECO was certainly a more feature-complete editor than Expensive Typewriter, so editing was much more efficient with TECO). The original PDP-1 version had no screen display. The only way to observe the state of the text during the editing process was to type in commands that would cause the text (or portions thereof) to be typed out on the console typewriter. By 1964, a special Version of TECO (TECO-6) had been implemented on the PDP-6 at MIT. That version supported visual editing, using a screen display that showed the contents of the editing buffer in real time, updating as it changed. Amongst the creators of TECO-6 were Richard Greenblatt and Stewart Nelson. At MIT, TECO development continued in the fall of 1971. Carl Mikkelsen had implemented a real-time edit mode loosely based on the TECO-6 graphic console commands, but working with the newly installed Datapoint-3300 CRT text displays. The TECO buffer implementation, however, was terribly inefficient for processing single character insert or delete functions—editing consumed 100% of the PDP-10. With Richard Greenblatt's support, in summer of 1972 Carl reimplemented