The History of Computers

1. The History of Computers

2. Reasons for learning how to use a computer • To develop problem-solving skills • To become aware of their capabilities and limitations • To develop an invaluable skill to be used at home and at work

3. 1.1 What is a Computer? • A machine that accepts information (called data), processes it according to specific instructions, and provides the results as new information. • Makes comparisons and decisions • Does not think it only acts on instructions given in the form a program • A program is set of instructions written in a special language that the computer understands.

4. 1.2 Ancient Counting Machines • Abacus- a device that aided calculations by sliding beads of different values on a frame History of the Abacus

5. 1.3 Arabic Numerals • Roman numerals replaced toward the end of the middle ages • Pencil and paper became more common than the abacus 2 +4 6

6. 1.4 Pascaline • 1642 Blaise Pascal invented one of the earliest mechanical devices for calculating • Made of a complicated set of gears • Could only add • Unreliable due to manufacturing problems Computer Museum of America

7. 1.5 The Stepped Reckoner • 17th Century Gottfried Wilhelm von Leibniz • Moveable carriage • Could add, subtract, multiply and divide • Unreliable due to manufacturing problems The Stepped Reckoner

8. 1.6 The Punched Card • 1810 Joseph Jacquard discovered that the weaving instructions for his looms could be stored on cards with holes punched in them • The idea that information could be stored by punching holes on a card was of great use in the later development of the computer. Jacquard’s Punched Card

9. 1.7 Babbage’s Difference and Analytical Engines • 1822 Charles Babbage • Difference Engine • Calculate numbers to the 20th place and print 44 digits per minute • Unreliable due to manufacturing problems • Analytical Engine • perform calculations based on program instructions entered using punched cards • Still unreliable • Used as a model for the modern computer

10. 1.8 Electronic Tabulating Machine • 1890 Herman Hollerith • Used electricity rather than mechanical gears • Used punch cards to determine when to open or close a particular circuit • For example - a closed circuit would increase the counter • Success - 6 weeks rather than 9 years to tabulate the census • Formed International Business Machines (IBM) Hollerith Electric Tabulating Machine

11. 1.9 The Mark I • 1930s mechanical adding machines were in use • Scientists needed machines that could act upon a decision; needed a computer rather than a calculator • Mark I 51 ft long, weighed 5 tons • Used relay switches • Still unreliable MARK I Story

12. 1.10 ENIAC: The First Electronic Computer • 1943 Electronic Numerical Integration and Calculator • 1500 sq ft, weighed 30 tons • Used vacuum tubes (17,000) • Was able to make decisions- first computer • Weaknesses • difficult to change instructions (3 days of changing wires) • tubes were constantly burning out MORE

13. 1.11 The Stored Program Computer • 1940s John von Neumann • Store computer instructions in Central Processing Unit (CPU), so instructions could simply be typed using a keyboard. • Computer function defined: • 1. Input data • 2. Store data while it is being processed • 3. Process data according to instructions • 4. Output the results • 1951 UNIVAC • large and expensive • 1000 calculations per second

14. 1.12 The Transistor • 1960’s IBM Model 650 • Transistors made computers smaller and less expensive • 10,000 calculations per second • Punched cards replaced by magnetic tape and reel-to-reel tape machines IBM 650

15. 1.13 Programming Languages • 1960s FORTRAN (FORmula TRANslator), COBOL (Common Business Oriented Language) • Developed because of the tedious task of typing 1s and 0s • 1 meant on for a switch and 0 meant off • Debug - removing errors from programs • Other Languages (C, Pascal, Ada)

16. 1.14 Integrated Circuits • Transistors replaced by chips • Blocks of silicon with logic circuits etched into their surfaces • Smaller • Cheaper • Faster • Decrease cost and size

17. 1.15 Mainframes • Large computer systems, very costly • Used by large corporations • Are accessed through terminals • keyboard and monitor

18. 1.16 The Microprocessor and the Microcomputer • 1970s Marcian Hoff Intel Corporation • CPU on a single chip • 1975 ALTAIR • 1977 Apple, Steven Jobs and Stephen Wozniak

19. 1.17 The Personal Computer • (PCs) Microcomputer low cost, fits on a desktop • Hardware • Monitor, CPU & Hard drive (inside base unit), Diskette Drive, CD-ROM Drive, Keyboard, Mouse • Software • programs that tell a computer what to do • Networked • microcomputers are connected so that data can be transmitted between them

20. 1.18 The Components of a Microcomputer

21. Input Devices: tools from which the computer can accept data • Keyboard • Disk drives • Mouse • Scanner

22. Memory: • Chips inside the computer where data can be stored electronically

23. Central Processing Unit (CPU): • A chip inside the computer that processes data and controls the flow of data between the computer’s other units. • Where the computer makes decisions.

24. Output devices: a device that displays or stores processed data • Monitors • Printers • Disk drives

25. Information Flow

26. 1.19 Memory • Read Only Memory (ROM) • Basic operating instructions for the computer • Permanent and cannot be changed • Random Access Memory (RAM) • Temporary • Where data and instructions can be stored

27. 1.20 The Central Processing Unit • Directs all the activities of the computer • Can only follow instructions • Arithmetic Logic Unit (ALU) can only add and compare numbers

28. 1.21 Bits and Bytes • 0=Off, 1=On • Binary because uses only 1 and 0 • Each 0 or 1 is called a bit (BInary digiT) • 8 bits = byte • ASCII (American Standard Code for Information Interchange) • each letter or symbol has a number which translates to the binary code • MB - megabytes or approx. million bytes • GB - gigabytes or approx. billion bytes • KB - kilobytes or approx. thousand bytes

29. 1.22 Storage Devices • Diskette made of mylar coated with a magnetic material and encased in hard plastic (1.44MB) capacity, read, write, delete • CD-ROM made of mylar with reflective coating sealed in clear hard plastic 600MB+, read only • Hard disk aluminum coated with a magnetic material, large storage capacity 1GB or more, read write, delete, permanently installed inside base unit

30. 1.23 Application Software • Written to perform specific applications or tasks • Common tasks include: word processing, spreadsheet and database • Also included in Microsoft Office is PowerPoint a presentation software

31. Word Processors • Allow users to enter text from the keyboard into a computer and then manipulate it electronically. • Word • Works • Word Perfect

32. Spreadsheets • Stores numeric data which can then be used in calculations • Excel • Lotus • Works

33. Databases • Allows users to store and manipulate large quantities of data using the computer. • Access • Works • DBase

34. Presentation Software • Allows users to combine text and graphics to create professional looking material to use in a presentation. • PowerPoint

35. Commonalities • Store data on a disk in a file (document) • a collection of data stored on a disk in a form the computer can read

36. 1.24 Advantages of a Computer • Reliable memory, with the ability to store and recall large amounts of data over long periods of time. • Speed, which enables it to process data quickly. • The ability to work 24 hours a day without rest.