QED (text editor)

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QED is a powerful line-oriented text editing program. The initial version was developed by Butler Lampson and L. Peter Deutsch (of Ghostscript fame) for the Berkeley Timesharing System running on the SDS 940. It was implemented by L. Peter Deutsch and Dana Angluin between 1965 and 1966.

It is primarily designed for maintaining multiple language source program files, such as MAC, NORD PL, FORTRAN or BASIC, though its convenience and ease of usage makes it suitable for all kinds of text editing.

QED (for "quick editor") addressed teleprinter usage, but systems "for CRT displays [were] not considered, since many of their design considerations [were] quite different".


The text being edited may be read from and written to any mass storage file or I/O device and text lines may be added, modified, replaced and deleted by a few easy-to-learn commands.

Lines of text may be addressed in several ways to make it easy for the user to position a specific line or a collection of lines where editing is to be performed. Positioning to a particular line may be specified in the commands themselves; however, just a line address itself can be a command to cause positioning to occur.

Other versions

Versions have since been written for many other systems, including CTSS, Multics, UNIX and various NORD computers.

The CTSS one was written by Ken Thompson, during the period when Bell Labs was involved in Multics (the Multicians started by using CTSS to host their work). Ken added regular expression support to his version; the first version of QED to have such, and one of the first uses of regular expressions. It was later ported to Multics, in BCPL, by Ken and Dennis Ritchie. (The primary Multics editor for many years, 'qedx', was based on the Multics QED.)

QED has also exerted strong influence on a number of other editors, such as UNIX's 'ed'.

NORD version

The NORD QED is a re-implementation originally by Bo Lewendal at Norsk Data. It was originally implemented for the NORD-1 in 1971. (This according to an ND employee who watched it happen at the time.)

External links