Mikial Singh Nijjar | The Definition of Computer Science
- 1. 1 The Definition of Computer Science Mikial Singh Nijjar
- 2. Objectives After studying this chapter, students will be able to: • Understand the definition of computer science • Write down everyday algorithms and evaluate them to determine if they are ambiguous or not effectively computable 2
- 3. Objectives (continued) After studying this chapter, students will be able to: • Understand the roots of modern computer science in mathematics thousands of years old and in mechanical machines hundreds of years old • Summarize the key points in the historical development of modern electronic computers • Map the organization of the text onto the definition of computer science 3
- 4. Introduction • Misconceptions – Computer science is: • The study of computers • The study of how to write computer programs • The study of the uses and applications of computers and software 4
- 5. The Definition of Computer Science • Computer science is the study of algorithms, including: – Their formal and mathematical properties – Their hardware realizations – Their linguistic realizations – Their applications 5
- 6. The Definition of Computer Science (continued) • Algorithm – Informally, “an ordered sequence of instructions that is guaranteed to solve a specific problem.” • Operations used to construct algorithms – Sequential operations – Conditional operations – Iterative operations 6
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- 9. The Definition of Computer Science (continued) • Why are formal algorithms so important in computer science? – If we can specify an algorithm to solve a problem, then we can automate its solution • Computing agent – Machine, robot, person, or thing carrying out the steps of the algorithm • Unsolved problems – Some problems are unsolvable, some solutions are too slow, and some solutions are not yet known 9
- 10. Algorithms • The Formal Definition of an Algorithm – A well-ordered collection of unambiguous and effectively computable operations that, when executed, produces a result and halts in a finite amount of time 10
- 11. Algorithms (continued) • Well-ordered collection – Upon completion of an operation we always know which operation to do next • Ambiguous statements – Go back and do it again (Do what again?) – Start over (From where?) 11
- 12. Algorithms (continued) • Unambiguous operation, or primitive – Can be understood by the computing agent without having to be further defined or simplified • It is not enough for an operation to be understandable – It must also be doable (effectively computable) by the computing agent 12
- 13. Algorithms (continued) • Algorithm – Result must be produced after the execution of a finite number of operations – Result may be a number, text, a light, picture, sound, or a change in the computing agent’s environment • Infinite loop – Runs forever – Usually a mistake 13
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- 16. Algorithms (continued) • The Importance of Algorithmic Problem Solving – “Industrial revolution” of 19th century • Mechanized and automated repetitive physical tasks – “Computer revolution” of the 20th and 21st centuries • Mechanized and automated repetitive mental tasks • Through algorithms and computer hardware 16
- 17. A Brief History of Computing The Early Period: Up to 1940 • Seventeenth century: automation/simplification of arithmetic for scientific research – John Napier invented logarithms as a way to simplify difficult mathematical computations (1614) – The first slide rule appeared around 1622 – Blaise Pascal designed and built a mechanical calculator named the Pascaline (1672) – Gottfried Leibnitz constructed a mechanical calculator called Leibnitz’s Wheel (1674) 17
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- 19. A Brief History of Computing The Early Period: Up to 1940 (continued) • Seventeenth century devices – Could represent numbers – Could perform arithmetic operations on numbers – Did not have a memory to store information – Were not programmable (a user could not provide a sequence of actions to be executed by the device) 19
- 20. A Brief History of Computing The Early Period: Up to 1940 (continued) • Nineteenth century devices – Joseph Jacquard designed an automated loom that used punched cards to create patterns (1801) – Herman Hollerith (1880s on) • Designed programmable card-processing machines to read, tally, and sort data on punched cards for the U.S. Census Bureau • Founded company that became IBM in 1924 20
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- 22. A Brief History of Computing The Early Period: Up to 1940 (continued) • Charles Babbage – Difference Engine designed and built in 1823 • Could do addition, subtraction, multiplication, and division to six significant digits • Could solve polynomial equations and other complex mathematical problems – Analytical Engine, designed but never built • Mechanical, programmable machine similar to a modern computer 22
- 23. A Brief History of Computing The Early Period: Up to 1940 (continued) • Nineteenth century devices – Were mechanical, not electrical – Had many features of modern computers: • Representation of numbers or other data • Operations to manipulate the data • Memory to store values in a machine-readable form • Programmable: sequences of instructions could be pre-designed for complex operations 23
- 24. A Brief History of Computing The Birth of Computers: 1940–1950 • Mark I (1944) – Electromechanical computer used a mix of relays, magnets, and gears to process and store data • Colossus (1943) – General-purpose computer built by Alan Turing for British Enigma project • ENIAC (Electronic Numerical Integrator and Calculator) (1946) – First publicly known fully electronic computer 24
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- 26. A Brief History of Computing The Birth of Computers: 1940–1950 (continued) • John Von Neumann – Proposed a radically different computer design based on a model called the stored program computer – Research group at the University of Pennsylvania built one of the first stored program computers, called EDVAC, in 1951 – UNIVAC-1, a version of EDVAC, first commercially- sold computer – Virtually all modern computers use the Von Neumann architecture 26
- 27. A Brief History of Computing The Modern Era: 1950 to the Present • First generation of computing (1950-1957) – Similar to EDVAC – Vacuum tubes for processing and storage – Large, expensive, and delicate – Required trained users and special environments • Second generation (1957–1965) – Transistors and magnetic cores instead of vacuum tubes – Era of FORTRAN and COBOL: high-level programming languages 27
- 28. A Brief History of Computing The Modern Era: 1950 to the Present (continued) • Third generation (1965 to 1975) – Era of the integrated circuit – Birth of the first minicomputer: desk-sized, not room-sized computers – Birth of the software industry • Fourth generation (1975 to 1985) – The first microcomputers: desktop machines – Development of widespread computer networks – Electronic mail, graphical user interfaces, and embedded systems 28
- 29. A Brief History of Computing The Modern Era: 1950 to the Present (continued) • Fifth generation (1985–?) – Massively parallel processors capable of quadrillions (1015) of computations per second – Handheld digital devices – Powerful multimedia user interfaces incorporatng sound, voice recognition, images, video, television – Wireless communications – Massive storage devices – Ubiquitous computing 29
- 30. Organization of the Text 30 Computer science is the study of algorithms including: Levels of the text: 1. Their formal and mathematical properties, Level 1: The Algorithmic Foundations of Computer Science 2. Their hardware realizations, Level 2: The Hardware World Level 3: The Virtual Machine 3. Their linguistic realizations, Level 4: The Software World 4. Their applications. Level 5: Applications Level 6: Social Issues
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- 32. Summary • Computer science is the study of algorithms • An algorithm is a well-ordered collection of unambiguous and effectively computable operations that, when executed, produces a result and halts in a finite amount of time • If we can specify an algorithm to solve a problem, then we can automate its solution • Computers developed from mechanical calculating devices to modern electronic marvels of miniaturization 32
- 33. About the Presentation • All chapter objectives are listed in the beginning of each presentation. • You may customize the presentations to fit your class needs. • A complete set of images from the book can be found on the Instructor Resources disc or the Instructor Companion site at login.cengage.com 33
- 34. Thank You 34