Computers and Computer Systems III

THE FIRST THREE GENERATIONS OF COMPUTERS.

The first commercially successful computer was the UNIVAC I, a name derived from "universal automatic computer," introduced by Remington Rand Inc. in 1951. It was based on Mauchly and Eckert's second computer, the ED VAC (from "electronic discrete variable automatic computer"), after the researchers had sold Remington Rand the rights to their invention. EDVAC used instruction cards developed by mathematician John von Neumann (1903-1957), and thus became one of the first computers with stored programs. Again, there were other contenders for this title, including another machine developed in Britain. Some believe that the ability to store programs is a defining characteristic of computers, and thus earlier machines like ENIAC don't qualify as computers. However, like ENIAC, UNIVAC and other first-generation computers used vacuum tubes as their primary switching components, and memory devices were made from magnetic drums and thin tubes of liquid mercury. The U.S. Census Bureau took delivery in 1951 of the first UNIVAC machine, weighing 8 tons and consisting of 5,000 vacuum tubes, at a price tag of $159,000 (equivalent to over $1 million in current dollars). In 1954, General Electric Co. acquired the first UNIVAC for commercial purposes, using it to process payroll data.

Due to their high costs, the first computers were aimed at government and research markets, rather than general business and industry. This changed once International Business Machines Corp. entered the computer industry, for the company already had an established sales force and a commercial clientele through its business of leasing electric punched card tabulating machines. The IBM 650 computer, introduced in 1954, used existing IBM punched-card readers, punches, and printers, which its clients already had, and it was also affordable because businesses could lease it. The first business enterprises to rely on computers were those that needed to process large volumes of data, such as banks, insurance companies, and large retail operations. The 650 became the most widely used computer in the world by the end of the 1950s, with 1,800 systems installed, making IBM the world's leading computer manufacturer.

The invention of the transistor in 1947 provided a substitute for vacuum tubes in the second generation of computers. Consequently, the physical size of computer systems was reduced, and reliability improved markedly. Transistor-based computers weren't shipped in large quantity until 1959, however. Computers of this period all used magnetic-core storage systems for main memory. Some used magnetic drums or disks in addition to magnetic tape for auxiliary memory. Examples include the IBM 410 and the Honeywell 800.

The third generation of computers, dating from the mid-1960s to the mid-1970s, used integrated circuits and large-scale integration, in which large quantities of transistors were put on a single wafer of silicon. They were also the first to use operating systems and database management systems. On-line systems were developed, although most processing was still done in batch mode. Examples of computers from this period included the IBM System/360 and 370, the Amdahl 470 V/6, the Control Data 6000 series, the Burroughs 5500, and the Honeywell 200. Amdahl Corp. was credited with reviving the industry in the 1970s by creating better and cheaper machines and spurring competitive developments by IBM and others.