APPENDIX
Analog computer operates by representing the variables of a problem by physical quantities easily generated or controlled, such as shaft rotations or electrical voltages. Between WW I and II, much work was done in developing the mechanical differential analyser, a close relation of the modern analog computer. In the period of years immediately following WW II, a tool - the electronic analog computer was developed. Two men - C.A. Lovell and D.B. Parkinson published use of operational amplifier as computer components. Their use of op-amps was in the computer of the M9 antiaircraft-gun director built by Western Electric Company.. Many companies have entered and left the analog computing field since its birth in 1948. By 1992, almost all purely analog computers had be replaced by hybrid or purely digital computers.
Digital computer is a computer that will accept data and information presented to it in its required, carry out arithmetic and logic operations on this raw material and then supply the required results in an acceptable form. (A digital computer counts and obeys logic rules exactly.) It can recognise only two states in any of its microscopic circuits : on or off, high or low voltage, or - 0 or 1. Computer speeds are measured in megaHertz, or millions of cycles per second.
Hybrid computer incorporating at least one stored-program digital program digital processor linked with a multiplicity of analog computing units. It have been successfully used since the late 1950’s for the many large industrial and government solution of a wide range of engineering simulation studies organisation with major research and development program have at least one active hybrid computing centre. In some fields, such as guided missiles and space vehicles where real-time, high fidelity simulation is essential, hybrid computers have been necessary for successful system development. The relative usefulness of continuous analog simulation versus numerical digital techniques has been subject to continuos review over the last 30 years. A hybrid computer capable of real-time solution has been less expensive than en equivalent digital computer. In certain real-time applications demanding unusually high frequency performance, no single digital computer is capable of the task. A new generation of automatic hybrid computing multiprocessor systems called SIMSTAR was introduced in 1983 by Electronic Associate. Combined digital and analog computing methods have proven to be very effective for a range of engineering studies over the last 30 years. The newest automatic hybrid multiprocessing systems have proven to follow the tradition of being the fastest available tool for real-time simulation of complex systems.
Information Processing Cycle Data is required for all computer processing. It refers to the raw facts (numbers and words), given to a computer during the input operation. In the processing phase, the computer manipulates the data in a predetermined manner to create information. Information refers to data that has been processes into a form that has meaning and is useful. The production of information by processing data on a computer is called information processing or electronic data processing. During the output operation, the information that has been created is put into some form, such as a printed report, that people can use. The information can also be stored in an electronic format for future use. For a computer to perform the operations in the information processing cycle, it must be given a detailed set of instructions or steps that tell it exactly what to do. These instructions can be called a program or software. Input devices They are used to enter data into a computer. A common input device is the keyboard. As the data is entered or keyed, it is displayed on a screen and stored in the computer.
Central Processor Unit (CPU) The CPU of a computer contains the electronic circuits that actually cause the processing of data to occur. All arithmetic and logical data processing takes place in the processor. Main memory(primary storage) is part of the CPU. Main memory electronically stores data and program instructions when they are being processed.
Output devices Output from a computer can be presented in many forms. Two most commonly used output devices are the printer and the screen (monitor).
Auxiliary storage units Auxiliary storage units store instructions and data when they are not being used by CPU. A common auxiliary storage device on personal computers is a disk drive, which stores data as magnetic spots on a small plastic disk called a diskette or floppy disk. Another auxiliary storage device is called a hard disk drive.
Microcomputers, also called personal computers(PC) are the small desktop-size systems that have become widely used in recent years. This category also includes laptop, portable and supermicro computers.
Minicomputers are more powerful than microcomputers and can support number of users performing different tasks. Originally developed to perform specific tasks such as engineering calculations. The most powerful "minis" are called superminicomputers.
Mainframe computers are large systems that can handle numerous users, store large amounts of data and process transactions at a very high rate. Mainframes usually require a specialised environment including separate air conditioning and electrical power.
Supercomputers the most powerful category of computers and accordingly, the most expensive. The ability of these systems to process hundreds of millions of instructions per second is used for such applications as weather forecasting, space exploration and other jobs requiring long, complex calculations.
EARLY HISTORY AND PIONEERS OF COMPUTERS
Abacus The abacus was the earliest and original mechanical counting device. It had been traced back at least 5000 years.
Pascaline Leonardo da Vinci (1452 - 1519) sketched ideas for a mechanical adding machine. A century and a half later, the French philosopher and mathematician Blaise Pascal (1623 - 1662) finally invented and built the first mechanical machine. It was called the Pascaline and used gear-driven counting wheels to do the addition.
Baggage’s Folly Charles Baggage (1973 - 1871), an English visionary and Cambridge professor advanced the state of computational hardware by inventing a "different engine", capable of computing mathematical tables. In 1834, while working on advances to the difference engine, Baggage conceived the idea of an "analytical engine". In essence, this was a general-purpose computer. As designed, his analytical engine would add, subtract, multiply and divide in automatic sequence at a rate of 60 additions per minute. The design called for thousands of gears and drives that would cover the area of a football field and be powered by a locomotive engine. Sceptics nicknamed his machine :"Babbage’s Folly". He worked on his analytical engine until his death. His detailed drawings described the characteristics embodied in the modern electronic computer.
The First Punch Card The Jacquard weaving loom, invented in 1801 by the French man Joseph-Marie (1753 - 1834) and still in use today, is controlled by punch cards. In the operation of Jacquard’s loom, holes are strategically punched in cards and the cards are sequenced to indicate a particular weaving design. In 1843, Lady Ada Augusta Lovelace suggested that cards could be prepared that would instruct Babbage’s analytical engine to repeat certain operations. Because of her suggestion, some people call Lady Lovelace the first programmer.
The Emergence of Automated Data Processing The U.S. Bureau of the Census commissioned Herman Hollerith, a statistician, to apply his expertise in the use of punch cards to take the 1890 census. With punched-card processing and Hollerith’s punched-card tabulating machine, the census was completed in just 3 years and saved the bureau over $5,000,000. Thus began the emergence of automated data processing. Hollerith founded Tabulating Machine Company and marketed his product all over the world. In, 1911, the Tabulating Machine Company merged with several other companies to form the Computing-Tabulating-Recording Company.
Electromechanical Accounting Machines In 1924, Hollerith’s company was renamed the International Business Machines Corporation (IBM). For decades, through the mid-1950s, punched technology improved with the addition of more punched-card devices and more sophisticated capabilities. Since each card usually contained a record, punched-card processing also became known as unit-record processing (one card equals one record). The electromechanical accounting machine (EAM) family of punched-card devices includes the card punch, verifier, reproducer, summary punch, interpreter, sorter, collator, calculator and the accounting machine. Most of these devices were "programmed" to perform a particular operation by the insertion of a prewired control panel.
Punched-card Processing A machine-room operator in a punched-card installation had a physically demanding job. Punched cards and printed output were moved from one device to the next on hand trucks. To prepare punched-card files for processing, the cards had to be sorted and collated. Because punch-card devices operate independently, several steps, called machine runs, are required to produce a given output.
Atanasoff and Berry An early patent on a device that most people thought to be the first electronic digital computer was invalidated in 1973 by a federal court ruling and Dr. John V. Atanasoff was officially credited with the invention of the electronic digital computer. Dr. Atanasoff, a professor at Iowa State University, developed the first electronic digital computer the year 1937 to 1942. He called his invention the Atanasoff-Berry Computer or ABC. A graduate student, Clifford Berry, was instrumental in helping him to build the ABC computer. The design of the ABC provided the foundation for the next advances in the development of the electronic digital computer.
Mauchly and Eckert Having the inspiration from ABC, Dr. John W. Mauchly collaborated with J. Presper Eckert, JR. To develop a machine that would compute trajectory tables for the U.S. army. The end product, a large-scale fully operational electronic computer, was completed in 1964 and called the ENIAC (Electronic Numerical Integrator and Computer). The ENIAC, built for World War II applications was completed in 30 months. A thousand times faster than its electromechanical predecessors, the ENIAC was a major breakthrough in computer technology. It could do 5000 additions per minute and 500 multiplications per minute. It weighed 30 tons and occupied 1500 square feet of floor space. The ENIAC operated in decimal and required 10 vacuum tubes, the ENIAC needed a great amount of electricity. Legend has it that the ENIAC, built at the University of Pennsylvania, dimmed the lights of Philadelphia whenever it was activated. The imposing scale and general applicability of the ENIAC signalled the beginning of the first generation of Computers.
The First Generation of Computers (1946 through 1959)
The UNIVAC I The first generation of computers was characterised by the most prominent feature of the ENIAC - vacuum tubes. Through 1950, several other notable computers were built, each contributing significant advancements, such as binary arithmetic, random access and the concept of stored programs. These computer concepts, which are common in today’s computers. The computer called the Universal Automatic Computer (UNIVAC I) was developed by Mauchly and Eckert for the Remington-Rand Corporation. By 1951, other manufacturers, primarily in the punched-card and electronics industries, were beginning to enter the commercial computer market. This group included Burroughs, Honeywell, International Business Machines (IBM) and Radio Corporation of America (RCA).
IBM Enters the Computer Market The first electromechanical computer called the Mark I, was the result of IBM-sponsored research .Howard Aiken, a Harvard University professor, completed the Mark I in 1944. The Mark I was essentially a serial collection of electronic calculators and had many similarities to Babbage’s analytical engine. IBM’s first entry into the commercial computer market was the IBM 701 in 1953. However, IBM 605 introduced in 1954 is probably the reason that IBM enjoys such a healthy share of today’s computer market. Unlike some of its competitors, IBM 650 was designed as a logical upgrade to existing punched-card machines.
The Computer Industry Comes of Aged By the late 1950s a number of new entrants, including Control Data Corporation (CDC), General Electric (GE) and National Cash Register (NCR) ventured into the computer industry.
The Second Generation of Computers (1959 through 1964)
The invention of Transistors signalled the start of the second generation of computers. The transistor meant more powerful, more reliable and less expensive computers that would occupy less space and give off less heat than did vacuum-tube-powered computers. The cost of a computer during the first, second and part of the third generations represented a significant portion of a company’s budget. Computers were expensive. Cost per instruction executed can be used to compare the cost of computers over the last 4 decades. Significant innovations, spurred by intense competition, have resulted in enormous increase in computer performance and substantial reductions in price. The dominant characteristics of the second generation were: 1. The transistor 2. Limited compatibility. Programs written for one computer usually required modification before they could run on a different computer. 3. Continued orientation to tape sequential processing 4. Low-level, symbolic programming languages
The Third Generation of Computers (1964 through 1971)
Characteristics What some computer historian consider to be the single most important event in the history of computers occurred when IBM announced their System 360 line of computers on April 7, 1964. The system 360 ushered in the third generation of computers. Integrated circuits did for the third generation. The System 360s and the third-generation computers of Honeywell, NCR, CDC, UNIVAC, Burroughs, GE and other manufacturers made all previously installed computers obsolete. The compatibility problems of second-generation computers were almost eliminated in third-generation computers. However, third-generation computers differed radically from second-generation computers. The change was revolutionary, not evolutionary. An important characteristic of third-generation computers was upward compatibility, which meant that a company could buy a computer from a particular vendor and then upgrade to a more powerful computer without having to redesign and reprogram existing information. Third-generation computers work so quickly that they provide the capability to run more than one program concurrently (multiprogramming). Although third-generation computers continued to provide tape-processing capabilities, the computer systems were developed to encourage the use of random professing and rotating magnetic disks.
The Minicomputer The demanded for small computers in business and for scientific applications was so great that several companies manufactured only small computers. These became known as minicomputers. Digital Equipment Corporation (DEC) and Data General Corporation took an early lead in the sale and manufacture of "minis".
The Forth Generation of Computers
The base technology of today’s computers is still the integrated circuit. This is not to say that three decades have passed without any significant innovations. In truth, the computer industry has experienced a mind-boggling succession of advances in the further miniaturisation of circuitry, data communications, the design of computer hardware and software and input/output devices.
The Microprocessor One of the most significant contributions to the emergence of the forth generation of computers is the microprocessor. The microprocessor, which can be contained on a single silicon chip, is a product of the microminiaturisation of electronic circuitry. The first fully operational microprocessor, sometimes called a " computer on a chip", was invented in 1971.
The Microcomputer The microprocessor is the processing component of the small, relatively inexpensive but powerful microcomputer. The microcomputer also called a personal computer, has made it possible for small businesses and individuals to own computers.
Laptop Laptop computers is small in size, light enough to be carried from place to place with relative ease and can be operated by an internal battery. Portable computers can be classified as palmtop computers, laptop(notebook) computers. The enabling for the laptop computer, the most prevalent type of portable computer include flat-panel displays, electronic and mechanical components that use very little power, and long-life, rechargeable batteries. Improvements in semiconductor fabrication-CMOS allowed the building IC components that required very small amount of electrical power and produced negligible amounts of heat. Besides, the visual display as improved dramatically in 1980s. LCD technology evolved from low-contrast, narrow viewing angle twisted-nematic LCDs in 1984, through supertwist LCDs in the late 1980s. Battery technology improved to keep pace with the increased power demand of high resolution displays. The nickel cadmium battery has become the standard in the 1990s because of its good weight-to-power ratio and nearly constant power output voltage regardless of charge,The Osborne 1 Portable, the first portable computer was introduced in 1981.