6. Computer system

1. 6. Computer system Reference: Discovering Computers 2003/2004 Course Technology, Thomson Learning Chapters 1, 3-8, 11.2-11.30

2. Computer System A computer system is made up of: • Hardwarerefers to the mechanical, electrical or electronic components of the computer system. • Core hardware: basic to the running of a computer system, e.g., CPU, RAM • Peripheral devices: for extended use, e.g., printer. • Software refers to the program that gives instructions on a computer system • System software: program used to control hardware or other software of a computer system. • Application software: program used by users to complete a particular task.

3. Outline • Computer system & peripheral devices S#4 – 40 • System Software & Application Software S#40 - 54 • Various applications & general knowledge S#55 - 70 1 3 2

4. Computer system & peripheral devices Reference Chapters 4 – 7, 1

5. Computer with peripheral devices PC camera, Modem (Communication) System Unit • Fig 1.5 Monitor (Output) Speaker (Output) Keyboard (Input) Printer (Output) Digital Camera (Input) (Processor, Memory and storage device) Scanner (Input)

6. Data representation in Computer • in digital form of 0 or 1 • e.g., 00110011 • 1 bit is the smallest unit • 8 bits grouped into 1 byte • Then, approximately • 1000 Byte = 1 Kilo Byte (KB or K) • 1000 Kilo Byte (KB or K) = 1 Mega Byte (MB) • 1000 Mega Byte (MB) = 1 Giga Byte (GB) • 1000 Giga Byte (GB) = 1 Tera Byte (TB)

7. Basic computer system (Ref: Chapter 4) Communication Device System Clock Input Unit Central Processing Unit Memory: RAM/ROM Storage Devices Arithmetic Logic Unit Control Unit Output Unit Note: Data on computer system includes program. Data flow line:

8. Instructions to the hardware by the system software • Input-Process-Output-Storage (IPOS) • Input is the acceptance of data by input device so that human data is translated into codes (e.g., alphabet into ASCII code) that computer systems can handle. • Process is the work done by CPU to transform the input data into the required form (e.g., text file, graphic file). • Outputis the result of process after the computer data has translated into different forms such as, text, graphics, audio and video result by output devices. • Storage is required to store data in digital form by permanent storage (e.g. floppy disk, hard disk, compact disk etc.)

9. System unit:Central Processing Unit(CPU) • to execute programs and process data • by • Arithmetic Logic Unit that performs basic operations in CPU, and • Control Unit that co-ordinates and controls the basic operations. • CPU’s speed relies on a system clock that generate the digital pulses • Therefore, processing speed is measured by clock speed in hertz. E.g., • (also known as processor) is the part of the computer system Micro-processor

10. System unit:Memory • also known as the main memory / primary memory of the computer system is used to hold programs and data for the CPU to process. • ROM (Read-Only-Memory) contains basic programs for processing (that is permanent memory = non-volatile memory). • RAM (Random Access Memory) contains data for processing (that disappears when power is off = volatile memory). • Ranging from MB to GB • Note: Insufficient RAM/ temporary memory space can slow down the computer processing

11. Peripheral devices: Storage (ref: Chapter 7) • e.g, hard disk drive, floppy disk drive for floppy disk, drive for compact disc and tape drive for tape • also known as secondary storage that is a permanent storage (outside the processor) • itpermanently stores data in digital form. (Remember: data here include program.) • it is much slower in read / write process (than primary memory - RAM) • as it requires drive for the read / write, it can also slow down the computer processing.

12. Storage medium : Common Examples Magnetic media using magnetic field E.g.,hard disk, floppy disks, tapes easier to re-write data Optical disks using optical laser E.g.,CD, VCD, DVD more difficult to re-write data Note: To combine both benefits, Magnetic Optical disks are used.

13. Storage devices: Details (I) • Hard drive for hard disk: • usually magnetic (but optically-assisted hard disk is developed to increase efficiency.) • can be fixed or removable • can use partitioning to separate compartments on the hard disk. (e.g., for installing multiple system software Win2000 and LINUX on the same computer). • Floppy disk drive for floppy disk • of magnetic media • can be write-protected to prevent accidental loss of data.

14. Storage devices: Details (II) <>Deleting: Deleted file can be recovered by program • Formatting is a process of preparing a floppy disk or hard disk for reading and writing (with the original contents on disk wiped out.) • Access of data for floppy disk and hard disk: by direct access by locating a item immediately. • Tape drive • for tape that can store large amount of data on magnetic-coated ribbon at a low cost • Access of data: by sequential access that move consecutively through stored items.

15. Storage devices: Details (III) • Different drives for different compact discs, also known as optical discs: • Access of data: by direct access • CD-ROM for read-only CD: • that cannot record/save any file (e.g. music CD) • Speed is denoted by: e.g., 52 X (original speed=150KB) • CD-RW (compact disc-rewritable): • also known as CD-R (compact disc-recordable) • onto which files can be recorded • DVD-ROM (digital versatile disc) • have very high storage capacities • and hence very suitable for files with multimedia effects stored

16. Other storage means: • Online storage through Internet access: • on web server • on web email server by e-mail attachment • Mobile storage: • that are usually used in handheld computer, digital camera and video camera. • on removable memory card or removable memory stick. • Smart card: • stores data on a microprocessor embedded in the card. • In addition to storing data, programs can be run carry out instructions i.e. processor / CPU e.g., Octopus Card

17. Input device (Ref:Chapter 5) • is any hardware component that allows you to enter data, command or simply user’s responses (e.g. to the dialogue box) into computer system. • including • Keyboard, • Pointing devices (e.g. mouse) • Scanning devices (e.g., image scanner) • Voice-input devices (e.g., microphone) • Visual input devices (e.g. digital camera)

18. (1) Input device: keyboard • is an input device that contains keys for entering data into computer • In addition to ordinary keyboard, there are • cordless keyboard that transmits data using wireless technology such as radio or light waves. • portable keyboard that can be attached and removed from a handheld computer. • ergonomic keyboard that has a design to reduce the chance of wrist injuries.

19. (2) Input: Pointing device (I) • is an input device that allows user to control a pointer on the screen. • including, • mouse: a pointing device for user to control the mouse pointer • E.g., mechanical mouse with the mouse-ball, optical mouse or cordless mouse

20. (2) Input: Pointing device (II) Touch screen: is a touch-sensitive display that can be input by touching with user’s finger. Light pen: is a handheld input device that contains a light source for inputting on screen. fig x 2 on 5.12

21. (2) Input: Pointing device (III) Digitizer (also known as a stylus): work with a digitizing tablet where the input movements are detected. Then, handwriting recognition software translates handwritten symbols into characters for the computer. Widely used in handheld computer Chinese handwriting recognition tablet: it still produces a list of possible words when the correct word is not exactly recognized. ie Tablet with handwriting recognition software

22. (3) Input: Scanning device (a) • Image scanner (also known as optical scanner): is a light-sensing input device that input the images of graphics and printed text into computer. • Scanningcan choose the settings of: • Resolution (Recall: the sharpness clearness of an image, in terms of number of pixels per area or practically dots per inch, dpi) • Number of colors (Recall: similar to grey-level, (28) 256 bits is less rich in color than (210) 1024 bits for colors)

23. (3) Input: Scanning device (b) • Scanned graphics can be edited by image processing software (e.g. Photoshop) for: • Re-sizing, • Re-coloring, • Addition of other graphic image • Further conversion into text document can be done by Optical Character Recognition (OCR) software: e.g., from scanned image to word document.

24. (3) Input: Scanning device (c) • Optical character recognition: is a technology that involves scanning image and translating the image into document file, such as word document. • Optical character recognition (OCR) device: includes an optical scanner for image input and • the OCR software: for analyzing it into document character (such as word document).

25. (3) Input: Scanning device (d) Optical Mark recognition (OMR) device: reads hand-written ink marks into computer for analysis, e.g. from multiple choice answer sheet. Bar code scanner: uses laser beams to read bar codes into computer. fig x 2 on 5.28

26. (4) Input: Voice input • Microphone: is a device to input sound into computer • Voice recognition (also called as speech recognition) software: to distinguish spoken words through microphone and translated to audio file by speech recognition software. • Generally, 2 different kinds of speech recognition software for: • discrete speech • or continuous speech.

27. (5) Input: Visual input • Digital camera: allows the user to take photo and store the image in digital form (instead of traditional film). • Digital video camera: records video in digital signals (but not necessarily for PC only). • PC Video Camera:is capturing video for PC(but not necessarily for transmission over the web). • Web camera:is basically for transmission of image over the web. • Note: Nowadays, these terms could mean the same thing as the product has all the features.

28. Output device (Ref: Chapter 6) • Output device is any hardware component that can convey information to the user by • Visual display device / Unit • Printer • Audio device / unit

29. Output:Visual display device • Output text, graphics, audio and video information in • color display or • monochrome display where • Gray scaling refers to using many shades of gray from white to black to improve contrast on images. Lower requirement of computer resources

30. Quality of Visual display device • Resolution: describe the sharpness clearness of an image, in terms of number of pixels per area. • The higher the resolution: the better the image’s quality. • E.g., 800 x 600 monitor can display 800 horizontal pixels and 600 vertical pixels. • Pixel Pitch: also called as dot pitch that is the distance between each pixel on display. • The lower the pixel pitch: the better the image’s quality. • Refresh rate: also called as vertical frequency or vertical scan rate that is the speed for redrawing images for screen. (Note) image can be affected/distorted when different aspect ratio in resolution is used: • Different resolutions: (800 x 600), (1024 x 768)  4:3 (no distortion); but if using 1280 : 1024  5:4 (distortion) can be measured by:

31. Visual Display Device: Monitor • Cathode Ray Tube Monitor: • Images produced by pixels that are created by electron beam • A small amount of electron magnetic radiation is also produced. • Liquid crystal display Monitor: • uses liquid crystal to create pixels of an output image (without electron magnetic radiation). • typically used by handheld computer, notebook and cellular display, in addition of desktop computer. • Gas plasma Monitor: • uses gas plasma for creating pixels. • Images can be viewed under strong light.

32. Visual Display Unit: Data Projector • takes image from a computer screen and projects it onto a large screen for audience • E.g., LCD Projector

33. Output:Printer • is an output device that produces text and graphics on paper or other printing material (such as film). • Impact printers: printing by striking against ink ribbon on paper. • only produces near-letter quality (but not real-letter quality nor graphics) • Non-impact printers: forms characters and graphic without striking on paper. • produces letter quality, and hence • Printer resolution measured by dots per inch (dpi) Lower quality with lower cost Higher quality with higher cost

34. Examples that you should know: Impact printers dot-matrix printer: with continuous form of paper; mainly for text only. Non-impact printers Ink-jet printer: forms characters and graphics by spraying tiny drops of liquid ink onto paper. Laser printer: creates images on paper using laser beam and toner higher speed than ink-jet printer plotter: produces high-quality printing in large scale. fig on 6.14 –17 fig on 6.22 - 28

35. Output: Audio device • is a component of a computer that produces music, speech or other sound. • Most common examples are: • Speakers • Headsets

36. Communication devices • refers to computer input or output for communicating in a network system • See in the class 7.Network System later on. Recall: modem for signal input and signal output in signal conversion.

37. Types of Computers (Ref:Chapter 1): Personal computer (desktop or notebook):the standalone computer or networked with other workstations Handheld computer:Portable that is usually fitting in one’s hand. by its purpose (a)

38. Types of Computers: by its purpose (b) • Mid-range server (computer) also known as minicomputer: supports up to hundreds and thousands of connected users at the same time, similar to mainframe but less powerful. • Mainframe computer (server computer): supports up to hundreds and thousands of connected users at the same time. • Supercomputers: consisting of hundreds of processors working in parallel, • supercomputers are suitable for scientific researches or applications such as weather forecasting that requires high processing speed and power.

39. System Software & Application Software Reference: Chapter 3.2-3.4, 8

40. System software (Ref: Chapter 8) • Examples: Win2000, DOS, UNIX, LINUX • consists of programs that control the operations of the computer resources (such as CPU time, memory) and its devices (such as printer) • acts as the intermediary layer • between users, application software (such as Office 2000) and the hardware of a computer. • For installing a system software: • CPU speed requirement • Hard disk storage requirement • RAM requirement and compatibility with other devices See Next Slide <> File compatibility

41. Types of system software • standalone operating system: e.g. Win2000 • on standalone computer, • on a workstation (i.e., computer connected to a server). • network system: • on server computer, e.g., Win2000 Server, UNIX, LINUX (although some can also run standalone computer.) • Embedded system: • on handheld computer (e.g. Pocket PC)

42. System Software (1) Operating System (2) Driver Program (3) Utility Program

43. (1) Operating System: (a) easy to operate • Users or application programs need not deal directly with hardware directly: • OS may communicate with hardware by the device driver program(S# 49). • OS may communicate with other computer resources (such as memory) for memory management between hard disk and RAM.

44. (1) Operating System:(b) easy to operate icon • If OS provides textmode interface, using command for instructions can be more efficient if the users know the commands well. (as it uses less computer resources) menu button • If OS provides Graphical User Interface (GUI)instead of textmode interface, it is easy for the user to operate.

45. (1) Operating System: (c)easy to maintain • Operating system • take care of any changes in the hardware by communicating with the device driver program. • detects the addition of a device, and automatically prompts the user for driver program installation of the device.) • It allows the plug-n-play technology • Plug-n-Play technology: saves the effort of configuration for adding hardware device into the computer system.

46. (1) Operating System: (d) Management of the system resources • Operating system acts as the manager to allocate system resource efficiently • to different programs (for standalone computer system): multi-tasking • to users (for network computer system): multi-users • by coordinating multiple processors on various jobs: multiprocessing. • so that no single program or single user can hold up a resource forever.

47. (1) Operating System: (e) More for network computer system • controlling network resources such as network printer, access to server • System administration for security: • such as logon and password system • restricting read or write access to some authorized users. (E.g., HSSC teachers have the right to save/write on M: while students can only read from M:)

48. (2) Driver Program • also known as device driver • tells the operating system how to communicate with hardware • E.g., printer driver, scanner driver etc.

49. (3) Utility programs • are included in the system software • can be classified as a part of system software as it performs a specific task to the system. • E.g., File viewer (i.e. Windows Explorer of MS Windows): • Viewing file information • Management of file attributes including: • 1) Read-Only • 2) Archive: indicated when the file is changed since last backup. • 3) Hidden: cannot be shown in the file viewer. • 4) Encrypted • 5) Compressed to a smaller size • (may need to be de-compressed for reading the file contents) • 6) Indexed: to facilitate searching in file viewer.

50. Some utility programs (you should know) As discussed above • File viewer (e.g. windows explorer): viewing file information • System trash program: holds for deleted files that can be recovered. • the system tool • such asscan disk to scan disk media for error. • backup: creates a copy of files on a hard disk in case the original is damaged. Work with Archive file attribute; See Also S#6 on p.2 of 3.ppt • Restore program: restore the backed up files to the original files in case the original got damaged. • performance monitor: reports about information of system resources such as memory or storage device. • disk defragmenter to re-arrange the disk space to eliminate fragmentation when files are stored in many scattered areas.