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

The 80×24 terminal display size became standard primarily due to IBM's market dominance, starting with the IBM 3270 terminal introduced in 1971, rather than technological constraints. The IBM PC later added one line to create the 80×25 standard. Various competing theories about aspect ratios, memory sizes, and TV scan rates are debunked by the wide diversity of terminal sizes that existed in the mid-1970s.