IBM, Sonic Delay Lines, and the History of the 80×24 Display
owl writes:
http://www.righto.com/2019/11/ibm-sonic-delay-lines-and-history-of.html
What explains the popularity of terminals with 80*24 and 80*25 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 80*24 display (the 3270) and it soon became the best-selling terminal, forcing competing terminals to match its 80*24 size. The display for the IBM PC added one more line to its screen, making the 80*25 size standard in the PC world. The impact of these systems remains decades later: 80-character lines are still a standard, along with both 80*24 and 80*25 terminal windows.
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.
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