1 / 68

6. Computer system

6. Computer system. Reference: Discovering Computers 2003/2004 Course Technology, Thomson Learning Chapters 1, 3-8, 11.2-11.30. Computer System. A computer system is made up of: Hardware refers to the mechanical, electrical or electronic components of the computer system.

powa
Télécharger la présentation

6. Computer system

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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.

More Related