Editing Dartmouth Time-Sharing System (section)

==User interface design==
Kemeny and Kurtz observed that "any response time which averages more than 10 seconds destroys the illusion of having one's own computer", so DTSS's design emphasized immediate feedback.{{r|dtss196810}} Many of its users thus believed that their [[computer terminal|terminal]] was the computer<ref name="ncc1974">{{Cite web |url=http://dtss.dartmouth.edu/transcript.php |title=Transcripts OF 1974 National Computer Conference Pioneer Day Session |website=Dartmouth Time Sharing System |publisher=Dartmouth College |year=1974}}</ref> and that, Kemeny wrote, "the machine is there just to serve him and that he has complete control of the entire system".{{r|dtssbrochure}}

Because of the educational aims, ease of use was a priority in DTSS design. It implemented the world's first [[Integrated Design Environment]] (IDE). Any line typed in by the user, and beginning with a line number, was added to the program, replacing any previously stored line with the same number; anything else was taken as a command and immediately executed.  Lines which consisted solely of a line number weren't stored but did remove any previously stored line with the same number. This method of editing provided a simple and easy to use service that allowed large numbers of [[teleprinter]]s as the terminal units for the Dartmouth Timesharing system.

IDE commands included

* '''CATALOG''' – to list previously named programs in storage
* '''LIST''' – to display the current program in memory
* '''NEW''' – to name and begin writing a program in memory
* '''OLD''' – to copy a previously named program from storage to memory
* '''RENAME''' – to change the name of the program in memory
* '''RUN''' – to compile and execute the current program in memory
* '''SAVE''' – to copy the current program from memory to storage
* '''SCRATCH''' – to clear the content of the current program from memory
* '''UNSAVE''' – to remove the current program from storage

These commands were often believed to be part of the BASIC language by users, but in fact they were part of the time sharing system and were also used when preparing [[ALGOL]]{{r|ncc1974}} or [[FORTRAN]] programs via the DTSS terminals.