10 Dec
1998
10 Dec
'98
9:37 p.m.
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.
Thanks in advance...
--------------------------------------------------------------------- O-
Uncle Roger "There is pleasure pure in being mad
roger(a)sinasohn.com that none but madmen know."
Roger Louis Sinasohn & Associates
San Francisco, California http://www.sinasohn.com/
11 Dec
11 Dec
6 a.m.
>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 (@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' ?)
Gruss
Hans
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
HRK
9:31 a.m.
Hans wrote:
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 ?
Well, maybe so, but I'm glad they *didn't* go with 40x12.
40 characters was chosen because it was the most that a typical television
(not monitor) in 1976 could display legibly. And even so, most color
televisions still had color fringes on the characters.
Eric
14 Dec
14 Dec
12:08 a.m.
> 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 ?
Well, maybe so, but I'm glad they *didn't* go
with 40x12.
40 characters was chosen because it was the most that
a typical television
(not monitor) in 1976 could display legibly.
64 by 20 would also have been a good choice - almost
the same ratio than 80x24 but with 256 lines (512 pixles)
still acceptable within TV limits.
(or 64x24 which is with 8x3 somewhat slim, but still
acceptable since within 33% of 5 by 2 (thats another
thumprule for characterdesign))
And even so, most color
televisions still had color fringes on the characters.
this is more to be put on the poor colour logic and
the low quality modulators used (and of course on NTSC :)
Gruss
Hans
--
Traue keinem Menschen der 5 Tage blutet und immer noch nicht tod ist.
8:59 a.m.
Hans wrote:
64 by 20 would also have been a good choice - almost
the same ratio than 80x24 but with 256 lines (512 pixles)
still acceptable within TV limits.
No. I've seen 64-column text on typical mid-70s NTSC televisions, and it was
abysmal. The televisions had to be modified to remove their color trap
in order to get reasonably sharp characters.
9:09 a.m.
At 07:59 PM 12/14/98 -0000, Eric Smith wrote:
No. I've seen 64-column text on typical mid-70s NTSC televisions, and it was
abysmal. The televisions had to be modified to remove their color trap
in order to get reasonably sharp characters.
I remember when the Amiga was first launched, its composite output
was purported to be able to drive 80 columns on an ordinary TV.
Was it a matter of televisions improving in the same time period,
or that they might've been talking about monochrome as opposed to
color? Certainly NTSC color has a hard time changing quickly, its
resolution is only a hundred or so lines across, isn't it, while
gray-scale resolution is as much four or five times that?
- John
11 a.m.
>No. I've seen 64-column text on typical
mid-70s NTSC televisions, and it was
>abysmal. The televisions had to be modified to remove their color trap
>in order to get reasonably sharp characters.
I remember when the Amiga was first launched, its
composite output
was purported to be able to drive 80 columns on an ordinary TV.
Was it a matter of televisions improving in the same time period,
or that they might've been talking about monochrome as opposed to
color?
Jep, thats the main thing I think. And 80 columes are also
hard for B&W TV - 80 columes with 8 bits per character gives
320 lines with less than 200 ns per line. Thats more than
5 MHz - and at 5 MHz the signal would be some sinus like
wave (a 'sawtooth' with heavy rounding), and the resulting
display would be more like gray - ok, of course letters
are not strict lines of black and white, so the resulting
might display characters (together with the highly sophisticated
patern matching machine called brain). For a B&W TV signal
some 200 Lines is a _VERY_ good result, so 80 chars with
6 pixles each (240 lines) might be well readable on a good TV.
Remember, these calculations are only minimal influenced with
the quality of a TV set, but rather fixed by TV modulation
schemes. you just can't fit a 10 MHz signal within a 5 MHz
chanal. Ok, to be honest, the numbers are based on european
TV, since I just can remember them without pain - 50 (half)
pictures per second, 625 lines per (full) picture, 15625
kHz line frequency, 64 us per scan line ... (Just ask me
after beer number 10 :), but basicly the US system comes
to similar numbers when we are down to lines since the
bandwidthe (chanal) is the same.
Certainly NTSC color has a hard time changing
quickly, its
resolution is only a hundred or so lines across, isn't it, while
gray-scale resolution is as much four or five times that?
Jep, exactly - you have always to 'runn the colour cycle'
from one colour to the next, so you cant go from bright
yellow to blue without crossing some other colours - and
the speed to go around the cycle is the maximum frequency
of the colour signal.
Gruss
H.
--
Der Kopf ist auch nur ein Auswuchs wie der kleine Zeh.
H.Achternbusch
10:23 a.m.
> 64 by 20 would also have been a good choice -
almost
> the same ratio than 80x24 but with 256 lines (512 pixles)
> still acceptable within TV limits.
No. I've seen 64-column text on typical mid-70s
NTSC televisions, and it was
abysmal. The televisions had to be modified to remove their color trap
in order to get reasonably sharp characters.
(Please, notice, I havn't talked about Colour TV)
First, basicly 70's tv had the same specs than todays.
And second 64 colume _and_ in colour _and_ NTSC ?
Say, do you still belive in the child, bringing all
the gifts ? (Or in Santa, to mention the US variant ?)
For NTSC is even 40 Columes hard to display, since a
yellow to blue change and back (for example, to take
a often used foreground/background) can be done 160
times within one scan line - but nothing else - you
will just get a kind of glowing screen. But thats not
a problem of using a TV set, thats a problem of the
NTSC colour signaling.
And if we talk about a 1976 design of a text screen,
the natural CRT would be a B&W set - still around
this time, the majority of all sold TV sets have
been B&W.
Gruss
Hans
--
Ich denke, also bin ich, also gut
HRK
1:19 p.m.
I wrote:
No. I've seen 64-column text on typical mid-70s
NTSC televisions, and it was
abysmal. The televisions had to be modified to remove their color trap
in order to get reasonably sharp characters.
Hans replied:
(Please, notice, I havn't talked about Colour TV)
First, basicly 70's tv had the same specs than todays.
No. Modern TVs have *much* better Y/C separation. Even the sets without comb
filters still are better than the mid-70s sets. And the luminance bandwidth
of modern TVs is much improved. We're comparing average televisions from the
mid 70s and present, not top-of-the-line models.
Even monochrome monitors had the color trap, which is what prevented
legible text display of much more than 64 columns. And usually it was a
low-pass filter, rather than a notch filter. It never was a comb filter.
Besides which, mid-70s TVs, monochrome or not, simply were not designed for
the horizontal bandwidth needed for good text display.
Apple's choice of a 40-column display was entirely correct given that they
were originally marketing it to people who would use it with a television.
Inexpensive video monitors weren't yet available. Of my friends who bought
Apple ][ computers in the 1977 time frame, over half used the computer with
a television. Most of the rest used Sanyo 9-inch or 12-inch monochrome
monitors, and only a few used color monitors.
IIRC, the Sanyo 9-inch monochrome monitor cost over $300 in 1977.
Eric
15 Dec
15 Dec
2:23 a.m.
I wrote:
> No. I've seen 64-column text on typical mid-70s NTSC televisions, and it was
> abysmal. The televisions had to be modified to remove their color trap
> in order to get reasonably sharp characters.
Hans replied:
> (Please, notice, I havn't talked about Colour TV)
> First, basicly 70's tv had the same specs
than todays.
No. Modern TVs have *much* better Y/C separation.
Even the sets without comb
filters still are better than the mid-70s sets. And the luminance bandwidth
of modern TVs is much improved. We're comparing average televisions from the
mid 70s and present, not top-of-the-line models.
Please, I'm _NOT_ talking about the TV sets, I'm talking about
TV specs - the standards about the TV signal - and they haven't
changed for the basic B&W and colour signaly since the 70s.
[...]
Besides which, mid-70s TVs, monochrome or not, simply were not designed for
the horizontal bandwidth needed for good text display.
That has nothing to do with bandwide of the TV set - they where
able to work on and display the frequencies defined for TV, and
these are the limits - not the TV set - Even in the early 70's
B&W TV tubes and electronics where already better than needed
for the TV signal.
But if the signal definition doesn't allow a frequency high
enough for 80 columne display, no TV, not a 500 Mark nor a
10,000 Mark TV can display it. No cheap one from 1970 and
no SuperDuperHighThingy TV from 1998. You just can't stick
a 10 MHz signal within a 5 MHz chanal. The TV modulation
prohibits this.
Apple's choice of a 40-column display was entirely
correct given that they
were originally marketing it to people who would use it with a television.
Inexpensive video monitors weren't yet available. Of my friends who bought
Apple ][ computers in the 1977 time frame, over half used the computer with
a television. Most of the rest used Sanyo 9-inch or 12-inch monochrome
monitors, and only a few used color monitors.
I did the same - my first display on the Apple][ was a 1968
build B&W TV (our old family TV, I got it in 1975 after we
had our first colour TV).
IIRC, the Sanyo 9-inch monochrome monitor cost over
$300 in 1977.
Jep, the prices have been around this in Germany. A friend of
mine was lucky - he dumpster dived a scraped 13" survilanve
Monitor - The best screen in the neighborhood.
Gruss
H.
--
Ich denke, also bin ich, also gut
HRK
9357
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9 comments
4 participants
participants (4)
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eric＠brouhaha.com -
Hans.Franke＠mch20.sbs.de -
jfoust＠threedee.com -
sinasohn＠ricochet.net