Unit 1 Section A
Computer Overview
I. Introduction
A computer is an electronic device that can receive a set of instructions, or program, and then carry out this program by performing calculations on numerical data or by manipulating other forms of information.
The modern world of high technology could not have come about except for the development of the computer. Different types and sizes of computers find uses throughout society in the storage and handling data, from secret governmental files to banking transactions to private household accounts. Computers have opened up a new era in manufacturing through the techniques of automation, and they have enhanced modern communication systems. They are essential tools in almost every field of research and applied technology, from constructing models of the universe to producing tomorrow’s weather reports, and their use has in itself opened up new areas of conjecture. Database services and computer networks make available a great variety of information sources. The same advanced techniques also make possible invasions of personal and business privacy. Computer crime has become one of the many risks that are part of the price of modern technology.
II. History
The first adding machine, a precursor of the digital computer, was devised in 1642 by the French scientist, mathematician, and philosopher Blaise Pascal. This device employed a series of ten-toothed wheels, each tooth representing a digit from 0 to 9. The wheels were connected so that numbers could be added to each other by advancing the wheels by a correct number of teeth. In the 1670s the German philosopher and mathematician Gottfried Wilhelm Leibniz improved on this machine by devising one that could also multiply.
The French inventor Joseph-Marie Jacquard, in designing an automatic loom, used thin, perforated wooden boards to control the weaving of complicated designs. During the 1880s the American statistician Herman Hollerith conceived the idea of using perforated cards, similar to Jacquard’s boards, for processing data. Employing a system that passed punched cards over electrical contacts, he was able to compile statistical information for the 1890 United States census.
1. The Analytical Engine
Also in the 19th century, the British mathematician and inventor Charles Babbage worked out the principles of the modern digital computer. He conceived a number of machines, such as the Difference Engine, that were designed to handle complicated mathematical problems. Many historians consider Babbage and his associate, the mathematician Augusta Ada Byron, the true pioneers of the modern digital computer. One of Babbage’s designs, the Analytical Engine, had many features of a modern computer. It had an input stream in the form of a deck of punched cards, a “store” for saving data, a “mill” for arithmetic operations, and a printer that made a permanent record. Babbage failed to put this idea into practice, though it may well have been technically possible at that date.
2. Early Computers
Analogue computers began to be build in the late 19th century. Early models calculated by means of rotating shafts and gears. Numerical approximations of equations too difficult to solve in any other way were evaluated with such machines. Lord Kelvin built a mechanical tide predictor that was a specialized analogue computer. During World War I and II, mechanical and, later, electrical analogue computing systems were used ad torpedo course predictors in submarines and as bombsight controllers in aircraft. Another system was designed to predict spring floods in the Mississippi River basin.
3. Electronic Computers
During World War II, a team of scientists and mathematicians, working at Bletchley Park, north of London, created one of the first all-electronic digital computers: Colossus. By December 1943, Colossus, which incorporated 1,500 vacuum tubes, was operational. It was used by the team headed by Alan Turing, in the largely successful attempt to crack German radio messages enciphered in the Enigma code.
Independently of this, in the United States, a prototype electronic machine had been built as early as 1939, by John Atanasoff and Clifford Berry at Iowa State College. This prototype and later research were completed quietly and later overshadowed by the development of the Electronic Numerical Integrator And Computer (ENIAC) in 1945. ENIAC was granted a patent, which was overturned decades later, in 1973, when the machine was revealed to have incorporated principles first used in the Atanasoff-Berry Computer.
ENIAC contained 18,000 vacuum tubes and had a speed of several hundred multiplications per minute, bur originally its program was wired into the processor and had to be manually altered. Later machines were build with program storage, based on the ideas of the Hungarian-American mathematician John von Neumann. The instructions, like the data, were stored within a “memory”, freeing the computer from the speed limitations of the paper-type reader during execution and permitting problems to be solved without rewiring the computer.
The use of the transistor in computers in the late 1950s marked the advent of smaller, faster, and more versatile logical elements than were possible with vacuum-tube machines. Because transistors use much less power and have a much longer life, this development alone was responsible for the improved machines called second-generation computers. Components became smaller, as did inter-component spacings, and the system became much less expensive to build.
4. Integrated Circuits
Late in the 1960s the integrated circuit, or IC, was introduced, making it possible for many transistors to be fabricated on one silicon substrate, with interconnecting wires plated in place. The IC resulted in a further reduction in price, size and failure rate. The microprocessor became a reality in the mid-1970s with the introduction of the large-scale integrated (LSI) circuit and, later, the very large-scale integrated (VLSI) circuit (microchip), with many thousands of interconnected transistors etched into a single silicon substrate.
To return, then, to the switching capabilities of a modern computer: computers in the 1970s were generally able to handle eight switches at a time. That is, they could deal with eight binary digits, or bits, of data, at every cycle. A group of eight bits is called a byte, each byte containing 256 possible patterns of ONs and OFFs (or 1s and 0s). Each pattern is the equivalent of an instruction, a part of an instruction, or a particular type of datum, such as a number or a character or a graphics symbol. The pattern 11010010, for example, might be binary data–in this case, the decimal number 210–or it might be an instruction telling the computer to compare data stored in its switches to data stored in a certain memory-chip location.
The development of processors that can handle 16, 32, and 64 bits of data at a time has increased the speed of computers. The complete collection of recognizable patterns–the total list of operations– of which a computer is capable is called its instruction set. Both factors–the number of bits that can be handled at one time, and the size of instruction sets–continue to increase with the ongoing development of modern digital computers.
III. Hardware
Modern digital computers are all conceptually similar, regardless of size. Nevertheless, they can be divided into several categories on the basis of cost and performance: the personal computer or microcomputer, a relatively low-cost machine, usually of desktop size (though “laptops” are small enough to fit in a briefcase, and “palmtops” can fit into a pocket); the workstation, a microcomputer with enhanced graphics and communications capabilities that make it especially useful for office work; the minicomputer, generally too expensive for personal use, with capabilities suited to a business, school, or laboratory; and the mainframe computer, a large, expensive machine with the capability of serving the needs of major business enterprises, government departments, scientific research establishments, or the like (the largest and fastest of these are called supercomputers).
A digital computer is not a single machine: rather, it is a system composed of five distinct elements: (1) a central processing unit; (2) input devices; (3) memory storage devices; (4) output devices; and (5) a communications network, called a bus, which links all the elements of the system and connects the system to the external world.
IV. Programming
A program is a sequence of instructions that tells the hardware of a computer what operations to perform on data. Programs can be built into the hardware itself, or they may exist independently in a form known as software. In some specialized, or “dedicated”, computers the operating instructions are embedded in their circuitry; common examples are the microcomputers found in calculators, wristwatches, car engines, and microwave ovens. A general-purpose computer, on the other hand, although it contains some built-in programs (in ROM) or instructions (in the processor chip), depends on external programs to perform useful tasks. Once a computer has been programmed, it can do only as much or as little as the software controlling it at any given moment enables it to do. Software in widespread use includes a wide range of applications programs–instructions to the computer on how to perform various tasks.
V. Future Developments
There is active research to make computers out of many promising new types of technology, such as optical computers, DNA computers, neural computers, and quantum computers. Most computers are universal, and are able to calculate any computable function, and are limited only bu their memory capacity and operating speed. However, different designs of computers can give very different performance for particular problems; for example, quantum computers can potentially break some modern encryption algorithms (by quantum factoring) very quickly.
A computer will solve problem in exactly the way it is programmed to, without regard to efficiency, alternative solutions, possible shortcuts, or possible errors in the code. Computers programs that learn and adapt are part of the emerging field of artificial intelligence and machine learning. Artificial intelligence-based products generally fall into two major categories: rule-based systems and pattern recognition systems, Rule-based systems attempt to represent the rules used by human experts and tend to be expensive to develop. Pattern-based systems use data about a problem to generate conclusions. Examples of pattern-based systems include voice recognition, font recognition, translation and the emerging field of on-line marketing.