IBM’s place in Computer History

 No history of the computer can neglect the giant of the computer world, IBM, which has had such an impact on the computer industry. Although IBM grew out of the Computing-Tabulating-Recording Company (C-T-R) that was founded in 1911, its origin dates back to the 1880s. The C-T-R Company was the result of a merger between the International Time Recording Company (ITR), the Computing Scale Company of America, and Herman Hollerith's Tabulating Machine Company (founded in 1896). ITR was founded in 1875 by clock maker Willard Bundy who designed a mechanical time recorder. C-T-R was a holding company for other companies that produced components or finished products; for example, weighing and measuring machines, time recorders, tabulating machines with punch cards.

 In 1914 Thomas J Watson, Senior, left the National Cash Register Company to join C-T-R and soon became president. In 1917, a Canadian unit of C-T-R called International Business Machines Co. Ltd was set up. Because this name was so well suited to C-T-R's role, they adopted this name for the whole organization in 1924.

 In 1928, the capacity of a punched card was increased from 45 to 80 columns. IBM bought Electromatic Typewriters in 1933 and the first IBM electric typewriter was marketed two years later. Although IBM's principal product was punched card processing equipment, after the 1930s IBM produced their 600 series calculators.

 IBM’s first contact with computers was via its relationship with Aiken at Harvard University. In 1948 Thomas J. Watson Senior at IBM gave the order to construct the Selective Sequence Control Computer (SSEC). Although this was not a stored program computer, it was IBM's first step from the punched card tabulator to the computer. 

IBM under T. J. Watson Senior didn’t wholeheartedly embrace the computer revolution in its early days. However, it was T. J. Watson, Jr., who was responsible for building the Type 701 EDPM (electronic data processing machine) in 1953 to convince his father that computers were not a threat to IBM's conventional business. Only nineteen 701s were built; it was a binary fixed-point machine that used magnetic tape to store data.  The 700 series was successful and dominated the mainframe market for a decade and, by the 1960s, IBM was the most important computer manufacturer in the world. In 1956 IBM launched a successor, the 704 that was the world's first super-computer and the first machine to incorporate floating-point hardware (if you are willing to forget Zuse’s contribution). The 704 was largely designed by Gene Amdahl who later founded his own supercomputer company in the 1990s.

 Although IBM’s 700 series computers were incompatible with the punched card processing equipment, IBM created the 650 EDPM that was compatible with the 600 series calculators and used the same card processing equipment. This provided an upward compatibility path for existing IBM users – a process that was later to become commonplace in the computer industry

 IBM’s most important mainframe was the System/360 that was first delivered in 1965. This series was designed to suit both scientific and business applications. The importance of the 32-bit System/360 is that it was a member of series of computers, each with the same architecture (i.e., programming model) but with different performance; for example the System/360 model 91 was 300 times faster than the model 20. Each member of the System/360 was software compatible with all other members of the same series. Moreover, IBM developed a common operating system, OS/360, for their series. Other manufactures built their own computers that were compatible with System/360 and thereby began the slow process towards standardization in the computer industry. Incidentally, prior to the System/360 a byte referred to a 6-bit quantity rather than an 8-bit value. 

An interesting feature of the System/360 was its ability to run the operating system in a protected state, called the supervisor state. Applications programs running under the operating system ran in the user state. This feature was later adopted by Motorola’s 680x0 microprocessor series. 

In 1960 the Series/360 model 85 became the first computer to implement cache memory – a concept first described by Wilkes in 1965 [Wilkes65]. Cache memory keeps a copy of frequently used data in very high-speed memory to reduce the number of accesses to the slower main store. Cache memory has become one of the most important features of today’s high performance systems. By the early 1970s the Series/360 had evolved to include the virtual memory technology first used in the Manchester Atlas machine.  

IBM introduced one of the first computers to use ICs in the 1970s. This was the System/370 that could run System/360 programs and therefore maintain backward compatibility. 

In August 1980 IBM became the first major manufacturer to market a personal computer. IBM had been working on a PC since about 1979 when it was becoming obvious that IBM’s market would eventually start to come under threat from the personal computer manufacturers such as Apple and Commodore. IBM not only sold mainframes and personal computers – by the end of 1970s IBM had introduced the floppy disk, computerized supermarket checkouts, and the first automatic teller machines.

 We now take a slight deviation into microprogramming, a technique that had a major impact on the architecture and organization of computers in the 1960s and 70s. Microprogramming was used to provide members of the System/360 series with a common architecture.