EDT (text Editor) - Digital

Digital

EDT was a text editor that was developed by Digital Equipment Corporation (DEC) for use on its PDP-11 series of computers (including RSX-11, RSTS/E and RT-11), and later for its VAX/VMS series as well.

The editor contained both line mode commands and a screen based editor. In screen mode, the default action for the user was to directly update text as he or she typed, with special commands available by pressing keypad commands. Arrow keys allowed for simple navigation, while keypad commands allowed for more complex navigation and searches. As with many user interfaces developed around this time, EDT used the "Gold Key" style of input first developed for the WPS-8 word processing system. "Gold Key" editing used the PF1 keypad key as a meta key allowing the introduction of a wide variety of commands using both the keypad keys and keys on the main keyboard. Pressing the PF2 keypad key would give on-screen help on the keypad and other key combinations:

/-----------------------------------\ /-----------------------------------\ | ^ | DOWN | | | | | | FNDNXT | DEL L | | | | | | <---- | ----> | | GOLD | HELP | | | | | | | | LEFT | RIGHT | | | | FIND | UND L | | UP | v | | | |--------+--------+--------+--------| \-----------------------------------/ | PAGE | SECT | APPEND | DEL W | DELETE Delete character | | | | | LINEFEED Delete to beginning of word | COMMAND| FILL | REPLACE| UND W | BACKSPACE Backup to beginning of line |--------+--------+--------+--------| CTRL/A Compute tab level | ADVANCE| BACKUP | CUT | DEL C | CTRL/D Decrease tab level | | | | | CTRL/E Increase tab level | BOTTOM | TOP | PASTE | UND C | CTRL/K Define key |--------+--------+--------+--------| CTRL/R Refresh screen | WORD | EOL | CHAR | | CTRL/T Adjust tabs | | | | ENTER | CTRL/U Delete to beginning of line |CHNGCASE| DEL EOL| SPECINS| | CTRL/W Refresh screen |-----------------+--------| | CTRL/Z Exit to line mode | LINE | SELECT | | | | | SUBS | Press a key for help on that key. | OPEN LINE | RESET | | To exit, press the spacebar. \-----------------------------------/

Users could configure default actions or define key sequences for their editor by placing EDT commands in an initialization file which would be executed upon starting the editor.

DEC later developed TPU, a powerful language for designing text editors on its VMS systems. TPU was used to produce a new standard text editor, EVE, as well as to rewrite EDT. EVE included an emulator of the EDT screen mode keypad for the benefit of those who were used to particular key functions. Both EVE and the TPU implementation of EDT are still distributed with OpenVMS.