Up to the early 1960s, IBM's low-end and high-end systems were incompatible, so programs could not easily be transferred from one to another, and the systems often used completely different peripherals such as disk drives. IBM concluded that these factors were increasing its design and production costs for both hardware and software to a level that was unsustainable, and were reducing sales by deterring customers from upgrading. So in 1964, the company announced System/360, a new range of computers which all used the same peripherals and most of which could run the same programs.Chuck Boyer, The 360 Revolution
