Module 1: introduction to organization and architecture of computer  (Page 4/4)

This idea, known as the Stored-program concept , is usually attributed to the ENIAC designers, most notably the mathematician John von Neumann, who was a consultant on the ENIAC project. The idea was also developed at about the same time by Turing. The first publication of the idea was in a 1945 proposal by von Neumann for a new computer, the EDVAC (Electronic Discrete Variable Computer).

In 1946, von Neumann and his colleagues began the design of a new stored-program computer, referred to as the IAS computer, at the Princeton Institute for Advanced Studies. The IAS computer, although not completed until 1952, is the prototype of all subsequent general-purpose computers. [link] shows the general structure of the IAS computer. It consists of:

• A main memory, which stores both data and instructions.
• An arithmetic-logical unit (ALU) capable of operating on binary data.
• A control unit, which interprets the instructions in memory and causes them to be executed.
• Input and output (I/O) equipment operated by the control unit.

• Commercial Computers

The 1950s saw the birth of the computer industry with two companies, Sperry and IBM, dominating the marketplace.

In 1947, Eckert and Mauchly formed the Eckert-Maunchly computer Corporation to manufacture computers commercially. Their first successful machine was the UNIVAC I (Universal Automatic Computer), which was commissioned by the Bureau of the Census for the 1950 calculations. The Eckert-Maunchly Computer Corporation became part of the UNIVAC division of Sperry-Rand Corporation, which went on to build a series of successor machines.

The UNIVAC II, which had greater memory capacity and higher performance than the UNIVAC I, was delivered in the late 1950s and illustrates several trends that have remained characteristic of the computer industry. First, advances in technology allow companies to continue to build larger, more powerful computers. Second, each company tries to make its new machines upward compatible with the older machines. This means that the programs written for the older machines can be executed on the new machine. This strategy is adopted in the hopes of retaining the customer base; that is, when a customer decides to buy a newer machine, he is likely to get it from the same company to avoid losing the investment in programs.

The UNIVAC division also began development of the 1100 series of computers, which was to be its bread and butler. This series illustrates a distinction that existed at one time. The first model, the UNIVAC 1103, and its successors for many years were primarily intended for scientific applications, involving long and complex calculations. Other companies concentrated on business applications, which involved processing large amounts of text data. This split has largely disappeared but it was evident for a number of years.

IBM. which was then the major manufacturer of punched-card processing equipment, delivered its first electronic stored-program computer, the 701, in 1953. The 70l was intended primarily for scientific applications. In 1955, IBM introduced the companion 702 product, which had a number of hardware features that suited it to business applications. These were the first of a long series of 700/7000 computers that established IBM as the overwhelmingly dominant com­puter manufacturer.

The second generation: transistors

The first major change in the electronic computer came with the replacement of the vacuum tube by the transistor. The transistor is smaller, cheaper, and dissipates less heal than a vacuum tube but can be used in the same way as a vacuum tube to con­struct computers. Unlike the vacuum tube, which requires wires, metal plates, a glass capsule, and a vacuum, the transistor is a solid-state device, made from silicon.

The transistor was invented at Bell Labs in 1947 and by the 1950s had launched an electronic revolution. It was not until the late 1950s, however, that fully transisto­rized computers were commercially available. IBM again was not the first company to deliver the new technology. NCR and. more successfully. RCA were the front-run­ners with some small transistor machines. IBM followed shortly with the 7000 series.

The use of the transistor defines the second generation of computers. It has become widely accepted to classify computers into generations based on the fundamental hard­ware technology employed (Table 2.2). Each new generation is characterized by greater processing performance, larger memory capacity, smaller size than the previous one.

The 3th generation

A single, self-contained transistor is called a discrete component. Throughout the 1950s and early 1960s, electronic equipment was composed largely of discrete com¬ponents—transistors, resistors, capacitors, and so on. Discrete components were manufactured separately, packaged in their own containers, and soldered or wired together onto circuit boards, which were then installed in computers, oscilloscopes, and other electronic equipment. Whenever an electronic device called for a transistor, a little lube of metal containing a pinhead-sized piece of silicon had to be soldered to a circuit hoard. The entire manufacturing process, from transistor to circuit board, was expensive and cumbersome. These facts of life were beginning to create problems in the computer industry. Early second-generation computers contained about 10,000 transistors. This figure grew to the hundreds of thousands, making the manufacture of newer, more power¬ful machines increasingly difficult.In 1958 came the achievement that revolutionized electronics and started the era of microelectronics: the invention of the integrated circuit. It is the integrated circuit that defines the third generation of computers. Perhaps the two most important members of the third generation are the IBM System/360 and the DEC PDP-8.