IBM, sonic delay lines, and the history of the 80×24 display

What explains the popularity of terminals with 80×24 and 80×25 displays? A recent blog post “80×25” 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.

As noted, a follow-up to our earlier discussion.

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