Chapter 2 The development of computers

1. Chapter 2 The development of computers • Learning outcomes • Outline the history of computers • Explain Von-Neumann Architecture • Explain the advantage of using the binary system in computing and not the decimal one. cis110

2. Additional reading • Essential • Stallings (2003): Chapter 2.1 • Further reading • Brookshear (2003): Chapter 0.2 • Schneider and Gersting (2004): Chapter 1.4 cis110

3. Lesson plan • Introduction • Definition of a computer • History of computer machines. • Hardware and software • Compilers cis110

4. Introduction • Modern computers are: • Small, • Fast, • Can do different things • To understand how modern computers work • It is useful to know their development history • How is information represented ? • How is information stored? • How is information processed? cis110

5. What is a computer? cis110

6. What is a computer? • Human who performs calculations • Calculating machine • General problem solver • Machine that performs repeated operations • Machine that can be programmed to perform different operations cis110

7. Navigation problem • Originally, a word computer was assigned to humans who were employed to solve difficult equations such as computing tabulated values that could be used by navigators. • Humans implies mistakes. • Large fortune can lost. cis110

8. A computer is something that does arithmetic sums • Charles Babbage (mathematician) realised that a fortune can be saved if the production of these tables can mechanised. • There were a limited mechanic machines at that time • such as abacus (limited in its precision) • A Computer becomes: • Something that does arithmetic sums. cis110

9. A computer is something that can perform repeated operations. • In 1822 C. Babbage proposed: • A mechanical calculating device designed to repeatedly add large number. • A computer becomes: • something that can perform repeated operations without error. cis110

10. A computer is machine that can perform different tasks • 1833 • C. Babbage designed a machine that could perform different operations. Order of operation can be changed after. • A computer becomes: • A machine that can be programmed to perform different tasks. cis110

11. First programmer? • Lady Ada Lovelace • She met C. Babbage in 1833 • She then wrote a program for his machine. • She was the world’s first programmer ? • More about Ada Lovelace go to http://www.exeter.ac.uk/BABBAGE/ada.html cis110

12. Origin the word Algorithm? • The idea of a program or algorithm • was already known at that time. • The idea of Algorithm was introduced by: • Muhammad ibn Mūsā al-Khwārizm (Mathematician) (9th Century) • He worked in Baghdad at the time when it was the centre of scientific studies and trade • His work introduced Indian numerals and algebraic concepts • Father of Algebra • The word algorithm comes from the name al-Khwārizm cis110

13. Abacus machine (1) • First computer: Abacus A rack with a sliding beads. cis110

14. Abacus machine (2) • Emerged about 5,000 years ago in China. • Not an automated computer • Allows users to perform computations using a system of sliding beads arranged in a rack. • Only helps to remember the current state of calculation. cis110

15. Pascal’s System Gear Blaise Pascal(1623-1662) • It was developed by Blaise Pascal in 1642. • If is also known as • Pascal mechanical calculator • Pascaline • Pascal’s adder. • It is an 8 figure calculating machine • adding, • subtracting, and • carrying 10's, 100's, and 1000's • Limitations: addition and subtraction only. cis110

16. 8 movable dials Pascal’s System Gear • Uses a base of 10 • add sums up 8 figures. • When the10’s dial moves one revolution, the 100’s dial moves one notch. cis110

17. Gottfried Von Leibniz • Leibniz developed Pascal’s ideas. • In 1671, he introduced a new device called Step Reckoner. • The device can performs the followings: • Addition and subtraction • multiplication and division. • Evaluation of square roots by series of stepped additions. cis110

18. Babbage’s Difference Engine Charles Babbage(1791-1871) • It could compute tables of numbers for naval navigation, e.g. x2 for any value of x. This machine punched the result into a copper plate. • For more information about Babbage’s work go to: http://www.maxmon.com/1830ad.htm http://en.wikipedia.org/wiki/Charles_Babbage cis110

19. Electronic Numerical Integrator and Computer (ENIAC) • (1943-1946) by John Mauchly • ENIAC used vacuum tubes for number computation. • The switches between the vacuum tubes were able to represent 2 states: ON and OFF. • However, programming was done manually. cis110

20. 17,468 vacuum tubes 70,000 resistor 6,000 manual switches 30 tones weight Covers 167 square metres 160 kilowatts of electric power cis110

21. Von Neumann Machine • Invented in 1943 by John Von Neumann • First machine that could perform all operations electronically. • No manual switching between states is needed • It consists of : • A central processing unit • Memory as well as Input/Output devices • These were connected through a system bus (set of wires) cis110

22. Von Neumann architecture Main memory CPU Add. bus Data bus Control bus cis110

23. Industry Standard Architecture ISA & Binary System • John von Neumann’s architecture was also referred to as ISA machine • The ISA used vacuum tubes that were based on the binary system. • The invention of transistors in 1947 (semi-conductor with 2 states) favoured the binary system to the decimal one. cis110

24. Computers since the 1940’s • 1st generation (1943-59): Bulky machines using vacuum tubes. • 2ndgeneration (1959-65): Transistor-based machines with magnetic core memory, programmed with high level languages (e.g. Fortran or Cobol). • 3rd generation (1965-75): Integrated circuits. Operating systems permitting shared use of machines. • 4th generation (1975-85): Machines built with large-scale and very large-scale integrated circuits (VLSI), e.g. Microcomputers. Graphical User Interfaces (GUIs), networks • 5th generation (1985-present): Multimedia interfaces, mobile computing, parallel processing. Most of today’s computers also inherit the properties of 4th generation devices. cis110

25. Hardware and Software • Hardware: • the physical components of a machine. • Touchable • Software: • Instructions performed by a computer • Sequence of instructions that include • Conditional statements • Block of statements that are to be repeated cis110

26. Software Terminology • Program: • Set of instructions or rules that a computer can apply • Software consists of a set of programs • Application program: • An end-user employs, such word processor, web browser, etc.. • System programs: • Manages the running of applications, such as operating system. • Link between the application software and the hardware cis110

27. Compilers • Executable/Object Code: • It is expressed in machine code. • A language the machine hardware can understand • Source Code: • The text of a program written in high-level language. • Compiler: • Translates from source code to object code, machine code. cis110

28. Source code compiling Compiler Executable Code Basic Process of Compilation cis110

29. Files and directories • A file is collection of data (e.g. plain text document) • Directories: • A means of organizing files • Usually form a hierarchy • Root: • is the top directory in the hierarchy • (/ Unix and \ in Ms-dos). cis110

30. Computer Component • Most computers consist of: • Input/output devices: keyboard, mouse • Visual display units: screen • Graphical user interfaces: display on the screen that allows you to interact, e.g. by pointing, clicking, dragging. Objects that you see on screen, e.g. wastebasket, folders, symbols such as disk, scissors, etc. • CPU: processor (e.g. INTEL, ) – made out of silicon • Hard-drive (magnetic disk, now more than a Terabyte) • RAM (working memory, now more than a Gigabyte) • Cards, such as graphic cards, sound cards, Ethernet cards • Operating systems, e.g. UNIX, Linux, Windows, etc • Programmes (written in assembly language, Java, C, C++, Visual Basic, Python, Perl etc.) cis110