when was memory "above" the terminal screen invented?

[Paul Koning]

> On Dec 13, 2020, at 9:37 PM, Stan Sieler via cctalk <cctalk at classiccmp.org> wrote:
> 
> Hi,
> 
> First, apologies if I asked this years ago (I've searched my archives, no
> hits :)
> 
> When was the concept of memory "above" the screen invented for terminals?
> 
> I.e., previously displayed data that had scrolled up and off the screen ...
> but could be retrieved (usually by scrolling down).
> 
> (Sometimes called "scrollback", or "offscreen memory".)
> 
> (BTW, I'm talking about terminal-local memory, not a scrollback implemented
> by the computer to which the terminal is connected.)
> 
> The HP 2640A, 1974, had (IIRC) several pages of memory available ... the
> user could scroll
> backwards and see what had been on the screen before it scrolled off (as
> long
> as it hadn't been lost by having too much subsequent output).
> 
> I suspect the DEV VT100, 1978, had it, but I can't find definitive proof
> online (sure, I can find VT102 emulators that have scrollback, but reading
> an old VT102 manual doesn't make it clear that it has it.)

Definitely not any of the DEC plain terminals.  However, the VT71/t (a.k.a., VT72), an LSI-11 based smart terminal that did local editing of a whole file, had a lot of memory only a small part of which was displayed.  And before that was the VT20, a very similar device controlled by an 11/05 (one for two "heads").  The VT71 dates to around 1977.

Depending on how loose your definition of off-screen memory is, the console display of the CDC 6000 mainframes (from around 1965) might qualify.

	paul