EDT (Univac)


EDT is a text editor running on the Unisys VS/9 operating system using the UNIVAC Series 90 mainframe computers, and currently runs on the Fujitsu BS2000 mainframe computer and operating system. It was developed by RCA for the TSOS operating system for Spectra series mainframes. The RCA version was later sold to Sperry Univac, and was released for the VS/9 operating system.
The Univac/Fujitsu EDT editor is a line-based editor, in that it does not use function keys. Unlike editors such as Teco or Emacs, the program is always in text-entry mode, similar to today's word processors.
Commands are sent to the editor by typing in text in the same manner as entering regular text, but the first character of the line is the command symbol, which defaults to the at sign. When a line begins with an @, the remainder of the line is used as a text-editing command. To enter a line of text beginning with @ which is not an editor command, it is necessary to prefix the line with a second @ sign, in which case, the first @ will be stripped off, and the line taken as text rather than a command. It is also possible to issue a command that the command indicator be changed from @ to a different character. One use for this feature is to write scripts to have EDT perform various actions upon another file. The command set of the editor includes the ability to create unattended programmable editing sessions through the use of test, comparison, branch and looping functions.
If line numbers are not present in the original file, the editor supplies a pseudo-line number for use in editing each line. Because of the ISAM file format which supports an 8-character index key, line numbers consist of a floating-point number in the range of 0.0000 to 9999.9999. The usual line number supplied by EDT starts at 1.000 and is incremented by 1 as each new line was added. Lines can be inserted between other lines by using a fractional number as a command prefix. For example, line 1 of a file would be 1.0000, line 2 would be 2.0000, and to insert a line between 1 and 2, one could type @1.5: followed by the text of the line; the colon would be discarded and the line would be inserted at 1.5000, between 1 and 2. A renumber command is available to renumber all or part of the file.
Commands in EDT generally consist of a command, which may be followed by a range of line numbers that the command was to act upon, and a subfunction indicating how the command is to act. The range was either expressed as a single line number, a range of lines separated by a dash,, or a group of lines, each separated by a comma. Some symbols are available to represent various values, such as the ampersand "&" or the word "all" representing every line in the file.
For example, to alter every "To" in a document to the word "From" you would type in
@ON ALL CHANGE "To" TO "From"
or
@on & change "To" to "From"
followed by the transmit key, and the editor would perform the action. Editing was basically full-screen, with actions not taking place until the user pressed the transmit key, a procedure very similar to today's practice of entering text into an input box in a web page, with no action being taken until the user clicks on the submit button.
Univac/Fujitsu's EDT editor provides extremely powerful editing capabilities, including
Fujitsu's current release of EDT also supports Unicode, which did not exist when Univac released its version of EDT.