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  2. Introduction • After having an overview of computer systems, let us now move on to learn how they have evolved over the years, from a computer that filled a whole room to one which can fit in your hand.

  3. The History of Computers • The first electronic computers were produced around 1940s. This was after a gradual change from the traditional processing aids E.g. abacus, slide rule etc. Some of the saline historical events as concerns the research towards computers origination are described below.


  5. In 1614, logarithm as an aid of calculation was invented by a Scottish mathematician known as John Napier, who subsequently invented a rod of bones, the idea which was in use three years later after his logarithm invention and was employed in carrying out multiplications.

  6. Napier’s Bones

  7. In the year 1620, the slide rule was invented by William Oughtred an English man. • In 1623, the idea of using binary numbers to represent e.g. characters, what was described as the binary codes was invented by Francis Bacon. • In 1642, the calculating machine, which had both the ability to add and to subtract numbers, was invented by Blaise Pascal.

  8. Pascal’s calculating machine

  9. In 1671, a calculating machine which had got the capability to multiply and to divide numbers was invented by Gottfried Von Leibniz. • At around 1802, a Jacquard Loom was invented by Jacquard. The machine was used to store instructions for weaving on the punched cards. This formed the basis for the programmable computer.

  10. Jacquard Loom

  11. In 1822 Charles Babbage, a professor of mathematics invented the model for the difference machine, whose design he did not complete but he later in 1834 used the same idea to develop a general purpose calculator, whose design was very close to the design of the computer today. . He is usually referred to as the grandfather of computer science. He built a computer theoretically, but his ideas were too advanced for the available technology.

  12. Charles Babbage The grandfather of computers

  13. Between1847–54, George Boole discovered Boolean algebra, whose principles are the basis of today’s computer logic gates used as logical elements. • Around Mid 1880s the tabulator machine was discovered by the Herman Hollerith, the machine had the capabilities of detecting data stored in terms of punched holes on the cards. Hollerith’s company later became IBM of today.

  14. Data stored in punched cards or tape must be read and interpreted into an understandable language. His ideas contributed to the invention of punched card readers and paper tape readers used in the first generation of computer systems.

  15. Hollerith’s Machine

  16. In 1900, the magnetic storage media principles as on e.g. magnetic tapes was discovered by Valdemar Poulson. Magnetized storage is used a lot in computer systems. • At around 1906, thermionic valves was invented by the Lee de Forest. The valves were useful in the electronic logics implementation. This were used for internal storage of first generation computers.

  17. In 1937, Automatic Sequence Controlled Calculator (ASCC) was developed by Howard Aiken and IBM. In 1959, Aiken developed punched paper tape, to be used as an input medium. • In 1938, ClaudeShannon established how Boolean algebra could be applied in the design of the computer’s logical circuits. This concept is still used in present day computers.

  18. In 1941, the calculating machines, Z3 and Z4 were developed by Konrad Zuse and these machines had the ability to use programs. Lady Ada is claimed to possibly be the first programmer. Ada a programming language was named after her in honor of her contribution to computer programming concept.

  19. Aiken worked out a plan, to set mechanical calculators to work on mathematical problems in control sequences. He set up a project to develop the necessary equipment and with the support of International Business Machines Corporation and Harvard University, and assistance from four co-workers from IBM, he built the first computer.

  20. This machine, called International Business Machines Automatic Sequence, Controlled Calculator, and also known as the Harvard Mark 1 computer was presented to Harvard University in August 1944. It was the firstinformation processing machine and it was electrically powered.

  21. Aiken’s Machine

  22. In 1946, Electronic Numerical Integrator and Calculator (ENIAC) was in use, developed by Presper Eckert and John Mauchly. The machine used valves and consumed a lot of power. It was water cooled. It was huge, taking up the walls of a room, 20 x 40 feet in size. This was the first electronic computer.

  23. Figure ENIAC

  24. In 1946, Von Neumann gave a report on the design which forms the basis of today's computer. He demonstrated that one could encode instruction to the machine, in the same language used for the data it processed. This brilliant demonstration made it possible to mix instructions and data in the program as both could also be stored in the computer.

  25. John Von Neumann’s Machine

  26. All of the above had contribution to the present day computer which is being improved on as the time goes by. Their ideas are still being researched and used in computer systems.

  27. Computer Generations • Following the development of the first electronic computer in 1946, the historical events in respect of computer development are not considered individually or in terms of individual years but in classifications of durations of periods known as “generations”. A generation groups computers of like technological characteristics.

  28. The transition from one generation to another was, and is influenced by the amount of research towards further development of the computers, and the related facilities and concepts. • We shall now describe computer generations:

  29. First generation Computers • These were the earliest time computers, which were in use from around the mid 1950’s to late 1950,s. They used big physical devices in their circuitry and hence were very big in their physical size. Their circuits incorporated the thermionic valves, a non solid state electronic device as a major logic element.

  30. These computers • Consumed a lot of power generating a lot of heat and hence non-reliable as the circuitry components were prone to failure. • They had limited internal memory which was based on the use of delay lines • The processor worked at slow speed as compared to the speeds of the computers of today.

  31. Their design was based on the John Von Neumann’s recommendations. • Examples of the first generation computers are UNIVAC and a commercial computer known as Lyon’s Electronic Office (LEO).

  32. Second Generation Computers • These were computers of the closing of the 1950s to the early1960s which used transistors. • The transistors are relatively smaller than valves and consume comparatively less power and therefore, the resulting computers were more reliable and comparatively small in size.

  33. The transistors were based on the solid-state technology, where the electric pulses were not to flow through a vacuum as in the case of the thermionic valves of the first generation computers. • The second-generation computers’ internal storage was higher than those of the first generation computers. The core memory replaced the delay lines and the magnetic drums, the internal memory of the first generation computers.

  34. The second-generation processors operated at a comparatively higher speed than those of the first generation computers. • The design of these second generation computers/processor was on a family basis; that is one family of computers had a set of related technological characteristics.

  35. These computers had programming languages whose vocabularies are close to the human language, specifically the English language. Examples of the second-generation computers include IBM 300 Series and ATLAS.

  36. Third Generation Computers • The computers of this generation came into being towards the mid 60’s and they used integrated circuits to replace the second-generation computer physical transistors. • The integrated circuits combine several physical electronic components within a small crystal called the silicon chip (IC- Integrated Circuit).

  37. The resulting computer was reduced in sizes as compared to the second-generation computers. • The small circuitry that resulted, improved the processing speed for pulses as data pulses could flow faster from one module to another as compared to the flow within the larger circuits, where they travel considerable distances.

  38. The third generation computers had higher main memory capacity.. • These computers were of increased processing power as compared to the second-generation computers, and therefore, had the capability of holding more than one set of instructions (programs) – Multiprogramming. • Could support more than one user

  39. These computers had the capability to support communication facilities i.e. remote communication facilities. • Users could be in remote locations or the same location • Examples of such computers are ICL 1900 Series, IBM 360.

  40. Fourth Generation Computers • The fourth generation computers resulted from a modification of the third generation computer’s technology. The design of this computer is based on Large Scale Integration (LSI) of circuitry and Very Large Scale Integration (VLSI) of circuitry.

  41. This generation marked the origin of mini computers in use today. • The design of the fifth generation computers was based on the VLSI technology that gave rise to PCs. • The microcomputers are usually described as PCs or stand-alone or desk top computers because they were primarily to serve a single person at a time.

  42. Fifth Generation Computers • The fifth generation is still a state of the art of technology that relies on predictions and further technological refinements.

  43. Trends in Computer Technology The trend in the computer’s technological revolution can be summarized as follows: • Continual decrease in computer size • Improved speed and power of processing • Decrease in computer’s and its related facilities cost • Increase in the number of components per circuit (IC).

  44. Computer Classifications • Because of the variations in characteristics of computers, computers can be categorized by: (a) Data Manipulated • Analog computers • Digital computers • Hybrid computers

  45. (b) The purpose for which they are designed :- • General purpose computers • Special purpose computers • Dedicated Computers (c) The basis of price, size and capabilities • Main frame computers • Mini computers • Micro computers • Personal computers

  46. Classification of Computers by the Types of Data Manipulated • Analog computers perform arithmetic operations and logical comparisons by measuring changes in physical magnitudes such as, electronic voltage, pressure changes, and temperature changes.

  47. The application of analog computers is confined to specialized areas as in scientific or engineering experiments, manufacturing processes and military weapons. • The examples of analogue devices include thermometer and car speedometer.

  48. The output from the system may be in the form of a graph produced by a plotting pen or a trace on a cathode ray tube. Its output signals can be used directly to control the operation of some other machine or process.

  49. Digital computers are the most commonly used type of computers. Their arithmetic operations and logical comparisons are based on digits (1s and 0s) and on other characters that have been numerically coded. These computers can process both numeric and alphabetic or alphanumeric data. Memory sizes determines capability

  50. These types of computers are used in a wider cross section of the application areas such as scientific, industrial and most of the other computer based data processing applications. The digital computer also has a unique ability, and that is, storing large quantities of data.