Cross-posting this here because there's probably overlapping interest with
csa2 readers.

------------------------

IBM, sonic delay lines, and the history of the 80x24 display ============================================================
by Ken Shirriff

What explains the popularity of terminals with 80x24 and 80x25
displays? A recent blog post "80x25" motivated me to investigate
this. The source of 80-column lines is clearly punch cards, as
commonly claimed. But why 24 or 25 lines? There are many theories,
but I found a simple answer: IBM, in particular its dominance of the
terminal market. In 1971, IBM introduced a terminal with an 80x24
display (the 3270) and it soon became the best-selling terminal,
forcing competing terminals to match its 80x24 size. The display for
the IBM PC added one more line to its screen, making the 80x25 size
standard in the PC world. The impact of these systems remains decades
later: 80-character lines are still a standard, along with both 80x24
and 80x25 terminal windows.

http://exple.tive.org/blarg/2019/10/23/80x25/

In this blog post, I'll discuss this history in detail, including
some other systems that played key roles. The CRT terminal market
essentially started with the IBM 2260 Display Station in 1965, built
from curious technologies such as sonic delay lines. This led to the
popular IBM 3270 display and then widespread, inexpensive terminals
such as the DEC VT100. In 1981, IBM released a microcomputer called
the DataMaster. While the DataMaster is mostly forgotten, it strongly influenced the IBM PC, including the display. This post also studies
reports on the terminal market from the 1970s and 1980s; these make
it clear that market forces, not technological forces, led to the
popularity of various display sizes.

Some theories about the 80x24 and 80x25 sizes =============================================
Arguments about terminal sizes go back decades, [5] but the article
80x25 presented a detailed and interesting theory. To summarize, it
argued that the 80x25 display was used because it was compatible with
IBM's 80-column punch cards, [1] fits nicely on a TV screen with a
4:3 aspect ratio, and just fit into 2K of RAM. This led to the 80x25
size on terminals such as the DEC VT100 terminal (1978). The VT100's
massive popularity led to it becoming a standard, leading to the
ubiquity of 80x25 terminals. At least that's the theory.

It's true that 80-column displays were motivated by punch cards and
the VT100 became a standard, [2] but the rest of this theory falls
apart. The biggest problem with this theory is the VT100's display
was 80x24, not 80x25. [3] In addition, the VT100 used extra bytes of
storage for each line, so the display memory did not fit into 2K.
Finally, up until the 1980s, most displays were 80x24, not 80x25.

----

Read the rest of the article here: http://www.righto.com/2019/11/ibm-sonic-delay-lines-and-history-of.html

--- SoupGate-Win32 v1.05
* Origin: fsxNet Usenet Gateway (21:1/5)