IBM mainframes

In the early years (1950-1965) IBM made many models of mainframes, many of which were incompatible with each other. It had two main lines of models: one for data processing use, and another one for scientific use. The two lines were largely incompatible. This all changed with the introduction of the [System 360]? in 1965. The [System 360]? was a single series of models, largely compatible with each other, for both commercial and scientific use. The [System 360]? was later succeeded by the the [System 370]?, the [System 390]? and most recently the zSeries?.

The primary operating systems in use today on IBM mainframes include MVS (also called OS/390 or z/OS), VM/CMS (also called z/VM), VSE, TPF, ALCS, and most recently Linux. (A few systems also remain that run MUSIC/SP?). Historical operating systems for the [System 360]? and its successors have included OS/360, MFT, MVT and SVS.

Many of the pre-System 360 mainframes also had operating systems, but they were very rudimentary by today's standards.