24x80 Standard? (was: Re: HX20)

From: Hans Franke <Hans.Franke_at_mch20.sbs.de>
Date: Fri Dec 11 11:00:38 1998

> >In a windowy world there are still plenty of applications that do great
> >work with an 80X24 character (or much less) screen.

> I was asked this yesterday (sorta) -- Why the 80x24 standard of yore?

> I believe the 80 columns comes from the 80 column punched cards, but I
> can't remember where the 24 comes from.

No, it isn't this easy. First, early terminals had several formats
(like the Siemens 8150 with 54x18 char in 1972). Also there is a
bandwidth problem - for line displays (pixel) the minimum time
to go from black to white defines the wideth of a pixel, for vector
display the maximum of lenght of all vectors together is defined
by the luminescence time of the CRT and the drawing speed. More
vectors (letters visible) means lower intensity, since you can't
extend the luminiscence periode if you want a fast changes including
character delete or scrolling.

For a vector displays (with 1970s technology), a 2000 characters
displist results already in about a half second for screen
refresh. so 80x25 was more then the possible maximum.

For pixel displays the number of characters in a row is limited
by the number of pixels possible to show, if we assume 6 pixels
per character (this only allowes upper case letters) you get
480 pixels in a row - or more than 7 MHz pixel clock (_at_60 Hz
& ~250 rows)) - already hard to display for 1970s technology.

Now we could add more lines for display, od display the vectors
in a different ratio but this wouldn't enlarge the screen -
Basicly all CRTs are build with a form factor of or around 4 by 3.
Talkin this, and the fact that a letter has ratio of (a bit less
than) 5 by 2 to be 'well cuted' you get a 10 by 3 ratio for the
number of caracters in a row to the number of caracters in a columne.

So a 40x12 or a 80x24 similar gives a 'good' view (Just for us
ol'apple freaks, didn't the APPLE ][ 40x24 display look _very_
clumbsy ? And didn't the TRS-80 charset lookt a lot more 'slimline' ?)


P.S.: 10 by 3 or 16 by 5 (as in 80x25) isn't realy the question -
I just use always 10x3 since it is easyer to remember

Ich denke, also bin ich, also gut
Received on Fri Dec 11 1998 - 11:00:38 GMT

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