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• Computer is fast becoming the universal machine of the 21st century
• Early computers were large in size and too expensive to be owned by individuals. They could only be programmed by computer engineers. The basic applications were confined to undertaking complex calculations in science and engineering
• Today, computer is no longer confined the laboratory. Computers and indeed, computing have become embedded in almost every item we use. Computing is fast becoming ubiquitous
• Computer is capable of taking input data through the keyboard, storing the input data, processing it at the central processing unit (CPU) and giving out the result (output) on the screen or the Visual Display Unit (VDU)
• Data


  Facts about a person, object or place e.g. name, age, complexion, school, class, height etc.
• Information


  Processed data or a meaningful statement e.g. Net pay of workers, examination results of students, list of successful candidates in an examination or interview etc.
• Methods of data processing

  • Manual method
  • Mechanical method
  • Computer method
• Manual method


  • Cumbersome, tiresome, boring, frustrating and time consuming
  • Likely to be affected by human errors
  • Does not allow for the processing of large volume of data on a regular and timely basis
• Mechanical method


  • Routine in nature
  • Virtually no creative thinking
  • Noisy, hazardous, error prone and untidy
  • Does not allow for the processing of large volume of data continuously and timely
• Computer method


  • Data can be steadily and continuously processed
  • Operations are practically not noisy
  • Has a store where data and instructions can be stored temporarily and permanently
  • Errors can be easily and neatly corrected
  • Output reports are usually very neat, decent and can be produced in various forms
  • Accuracy and reliability are highly enhanced
• Characteristics of a computer

  • Speed
  • Accuracy
  • Storage
  • Automatic
  • Reliability
  • Flexibility
• Components of the computer system

  • Hardware
  • Software
  • Users
  • Computing environment
• Computer hardware


  • Input unit
  • Processing unit
  • Output unit
• Computer software


  • System software
  • Utility software
  • Application software
• Computer users


  • Expert users
  • Casual users
• Computing environment


  • Building and fittings
  • Furniture
  • Auxiliary devices
• The computer method of data processing is superior to the manual and mechanical methods of data processing
• The computing system is made up of the computer system, the users and the computing environment
• First Generation Electronic Computers

  1937 - 1953
• J. V. Atanasoff built an electronic computer in 1937 that could solve 29 simultaneous equations with 29 unknowns, but it was not programmable
• Colossus, designed by Alan Turing for the British military in 1943, played an important role in breaking codes used by the German army in World War II
• The first general purpose programmable electronic computer was the Electronic Numerical Integrator and Computer (ENIAC), built by J. Presper Eckert and John V. Mauchly at the University of Pennsylvania, completed in 1946
• The machine (Atanasoff-Berry computer) was not programmable, and was more of an electronic calculator
• Colossus


  An early electronic machine designed by Alan Turing for the British military in 1943 to break codes used by the German army in World War II
• Turing Machine


  A mathematical formalism widely used in the study of computable functions, proposed by Alan Turing
• The existence of Colossus was kept secret until long after the war ended, and the credit due to Turing and his colleagues for designing one of the first working electronic computers was slow in coming
• ENIAC


  The first general purpose programmable electronic computer, built by J. Presper Eckert and John V. Mauchly at the University of Pennsylvania
• Work on ENIAC began in 1943, funded by the Army Ordinance Department, which needed a way to compute ballistics during World War II. The machine wasn't completed until 1945, but then it was used extensively for calculations during the design of the hydrogen bomb. By the time it was decommissioned in 1955 it had been used for research on the design of wind tunnels, random number generators, and weather prediction
• EDVAC


  A new machine project started by Eckert, Mauchly, and John Von Neumann before ENIAC was finished, whose main contribution was the notion of a stored program
• There is some controversy over who deserves the credit for the stored program idea, but no one knows how important the idea was to the future of general purpose computers
• ENIAC was controlled by a set of external switches and dials; to change the program required physically altering the settings on these controls. These controls also limited the speed of the internal electronic operations. Through the use of a memory that was large enough to hold both instructions and data, and using the program stored in memory to control the order of arithmetic operations, EDVAC was able to run orders of magnitude faster than ENIAC
• By storing instructions in the same medium as data, designers could concentrate on improving the internal structure of the machine without worrying about matching it to the speed of an external control
• The EDVAC project is significant as an example of the power of interdisciplinary projects that characterize modern computational science. By recognizing that functions, in the form of a sequence of instructions for a computer, can be encoded as numbers, the EDVAC group knew the instructions could be stored in the computer's memory along with numerical data. The notion of using numbers to represent functions was a key step used by Goedel in his incompleteness theorem in 1937, work which Von Neumann, as a logician, was quite familiar with. Von Neumann's background in logic, combined with Eckert and Mauchly's electrical engineering skills, formed a very powerful interdisciplinary team
• Machine code


  The first programs were written out in machine code, i.e. programmers directly wrote down the numbers that corresponded to the instructions they wanted to store in memory
• Assembly language


  A symbolic notation used by programmers in the 1950s, which was then hand-translated into machine code
• Assemblers


  Later programs that performed the translation task from assembly language to machine code
• As primitive as they were, these first electronic machines were quite useful in applied science and engineering. Atanasoff estimated that it would take eight hours to solve a set of equations with eight unknowns using a Marchant calculator, and 381 hours to solve 29 equations for 29 unknowns. The Atanasoff-Berry computer was able to complete the task in under an hour. The first problem run on the ENIAC, a numerical simulation used in the design of the hydrogen bomb, required 20 seconds, as opposed to forty hours using mechanical calculators. Eckert and Mauchly later developed what was arguably the first commercially successful computer, the UNIVAC; in 1952, 45 minutes after the polls closed and with 7% of the vote counted, UNIVAC predicted Eisenhower would defeat Stevenson with 438 electoral votes (he ended up with 442)
• Second generation computers (1954-1962)


  Saw several important developments at all levels of computer system design, from the technology used to build the basic circuits to the programming languages used to write scientific applications
• Electronic switches in second generation

  • Based on discrete diode and transistor technology with a switching time of approximately 0.3 microseconds
• Memory technology in second generation


  Based on magnetic cores which could be accessed in random order, as opposed to mercury delay lines