IBM's first successful, commercial computer. Introduced in 1954, it read data from punch cards and magnetic tapes. By the end of the 1950s, there were more than 1,500 units installed, making it the most widely used computer in the world. The 650 added high-speed computational ability to the punch card data processing that was the norm in every large enterprise in those days. The 650 used a fixed-head magnetic drum that rotated at 12,500 RPM for its internal memory from 1,000 to 2,000 10-digit words. Magnetic disks, which IBM pioneered on its 305 RAMAC, were made available to the 650 in 1956. See IBM 701, IBM 1401 and System/360.