1964: Standardization Begins, Sort Of
The IBM 2311, introduced in 1964, was the second disk drive built for IBM's System/360 midrange computers, one of the most successful computers ever built.
Because of the variety of models in the System/360 family, the IBM 2311 was the first disk drive to be built with a standardized electrical connection, making it available across multiple versions of the computer.
That also made it possible for vendors other than IBM to look at manufacturing plug-compatible hard disks for IBM computers for the first time. Memorex was the first to do so, in 1968.