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The standard cursor movement keys on the TI-99/4, /4A and apparently /8 were Function + E (for up), S (for left), D (for right), and X (for down). These keys were also often used (without needing the function key) for games.

WordStar on CP/M used the same keys, albeit using Control rather than Function (as Function was a somewhat specific key to the TI keyboard). A number of other CP/M and early DOS applications copied the WordStar combinations, so they were quite common for a while.

Was this coincidental, did one of these copy the other, or did they both derive from some common older source that I'm not aware of?

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Was this coincidental, did one of these copy the other, or did they both derive from some common older source that I'm not aware of?

I wouldn't make a bet, but Wordstar is what I would have said as well.

But the combination itself is not just an invention out of nowhere, but follows a logic based on common keyboard layouts.

ESDX (and ESDF for games and DEC alike T-Bar cursors) is the first cursor like location that can be used across various keyboards. These letters are the same on English and German Keyboards (QWERTZ/QWERTY key order), an at least close to each other and also on the left side for French Keyboards (AZERTY). On terminals, where there is no scan code, but letters and letterwise assigned controll codes this avoides the need for country/keyboard dependant command routines - and equaly important manualy and key sheets. These three keyboard layouts cover a great deal in Europe and worldwide.

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  • Nowadays the tend to use WASD (pronounced waz dee) instead of ESDF. – cup Sep 16 '18 at 13:23
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    @cup: As stated in the answer, the idea was to create a layout that worked on various international keyboards. WASD doesn't form a proper layout on AZERTY keyboards. – DrSheldon Sep 16 '18 at 18:48
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    afaik WASD was introduced by quake? – Tommylee2k Sep 17 '18 at 13:39
  • True. Just, I tried to stay with the question, avoiding to go into a lengthy rant about cursor/fuction handling on alpha keyboards. – Raffzahn Sep 17 '18 at 13:49

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