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6. Computer system

Reference:Discovering Computers 2003/2004Course Technology, Thomson LearningChapters 1, 3-8, 11.2-11.30

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Computer SystemA computer system is made up of:

Hardware refers 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.

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OutlineComputer system & peripheral devices

S#4 – 40

System Software & Application Software S#40 - 54

Various applications & general knowledgeS#55 - 70

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2

3

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Computer system & peripheral devices

ReferenceChapters 4 – 7, 1

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Computer with peripheral devices

Fig 1.5Speaker (Output)

Scanner (Input)

Printer (Output)

Monitor (Output)

Keyboard (Input)

(Processor, Memory and

storage device)

PC camera, Modem (Communication)

Digital Camera (Input)

System Unit

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Data representation in Computer

in digital form of 0 or 1e.g., 001100111 bit is the smallest unit8 bits grouped into 1 byteThen, 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)

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System Clock

Basic computer system (Ref: Chapter 4)

Data flow line:

Input Unit

Output Unit

Central Processing Unit Memory:

RAM/ROM

Storage Devices

Communication Device

Control

Unit

Arithmetic Logic Unit

Note: Data on computer system includes program.

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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).

Output is 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.)

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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.,CPU SpeedPentium 4 1.4 GHz and upPentium III 400 MHz - 1.2 GHz

(also known as processor) is the part of the computer system Micro-processor

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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

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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 tapealso known as secondary storage that is a permanent storage (outside the processor)it permanently 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.

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Storage medium : Common Examples

Magnetic media using magnetic fieldE.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.

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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.

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Storage devices: Details (II)

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.

<>Deleting: Deleted file can be recovered by program

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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

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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 / CPUe.g., Octopus Card

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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)

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(1) Input device: keyboardis an input device that contains keys for entering data into computerIn 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.

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(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

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(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

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(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

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(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.Scanning can 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)

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(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.

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(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).

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(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

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(4) Input: Voice input

Microphone: is a device to input sound into computerVoice 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.

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(5) Input: Visual inputDigital 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.

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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

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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

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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:

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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.

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Visual Display Unit: Data Projectortakes image from a computer screen and projects it onto a large screen for audience

E.g., LCD Projector

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Output: Printeris 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

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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

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Output: Audio device is a component of a computer that produces

music, speech or other sound.

Most common examples are:SpeakersHeadsets

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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.

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Types of Computers (Ref: Chapter 1):

Personal computer (desktop or notebook): the standalone computer or networked with other workstationsHandheld computer: Portable that is usually fitting in one’s hand.

by its purpose (a)

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Types of Computers:

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.

by its purpose (b)

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System Software & Application Software

Reference:Chapter 3.2-3.4, 8

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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

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Types of system softwarestandalone 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)

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System Software

(1) Operating System(2) Driver Program(3) Utility Program

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(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.

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(1) Operating System: (b) easy to operate

If OS provides Graphical User Interface (GUI) instead of textmode interface, it is easy for the user to operate.

icon

button

menu

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)

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(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.

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(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.

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(1) Operating System: (e) More for network computer system

controlling network resources such as network printer, access to serverSystem 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:)

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(2) Driver Program

also known as device drivertells the operating system how to communicate with hardware E.g., printer driver, scanner driver etc.

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(3) Utility programsare included in the system softwarecan 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-Only2) Archive: indicated when the file is changed since last backup.3) Hidden: cannot be shown in the file viewer.4) Encrypted5) Compressed to a smaller size (may need to be de-compressed for reading the file contents)6) Indexed: to facilitate searching in file viewer.

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Some utility programs (you should know)

File viewer (e.g. windows explorer): viewing file information

System trash program: holds for deleted files that can be recovered.

the system tool such as scan disk to scan disk media for

error. backup: creates a copy of files on a hard

disk in case the original is damaged.

As discussed above

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.

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Note: Booting computer system

Cold boot refers to starting the whole process to get ready the hardware and loading the operating system from the hard disk of the computer by powering up.Warm boot refers to restarting the computer by loading the operating system from the secondary storage (such as hard disk) without powering up. Boot with boot disk if the boot program that load the operating system are stored on a diskette on CD_ROM drive or floppy disk drive instead of hard disk.

HW 2,3

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Application Softwareis the application program that runs on the system software, need to be system-compatible

e.g. MS Office Series on MS Windows Systems but not MS Office Series on LINUX

is a piece of software to let its user to complete a particular task for the user,

Examples: Word 97 for word processing, Visual FoxPro for database management.

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Applications in various industries

Chapter 3.7-3.37, 11.27-11.30

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Some categories of Application Software

Productivity applications: for business or personal usesIndustrial applicationsTelecommunication/ CommunicationsMultimedia applicationsEducationHomeArtificial Intelligence

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Application: Productivity (I)Word Processing (e.g. Microsoft Word) Also called as word processor: allows users to

create and manipulate documents that contains text and graphics.

Spreadsheet (e.g., Microsoft Excel) Organizes data in rows and columns so that data

calculation and what-if analysis can be performed.

Presentation Graphics (e.g. Microsoft PowerPoint) Organizes presentation into slides.

Database: (E.g., Microsoft Visual FoxPro) Collect and organize data in manner that allows

access, retrieval and updating of the data.

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Application: Productivity (II)Software Suite (E.g., Microsoft Office 2000): Also known as Integrated Software: is a

collection of individual applications sold as a single package.

Management software: for storage and analysis of management data such as accounting data related to ledgers and payroll etc.Project Management: allows the user to plan, schedule, track, and analyze the events, costs and other resources of a project (e.g., Microsoft Project)Personal Information Management: includes features for organizing personal data such as electronic calendar appointment, address book etc. (e.g., Organizer, Personal Data Assistant that may be run on handheld computer.)

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Industrial applicationsComputer Aided Design (CAD): allow users to design products on computer. (~~Recall the video)Computer Aided Engineering (CAE): allows users to simulate situations that test product designs. (~~Recall the video)Computer Aided Manufacturing (CAM): helps controlling the manufacturing equipmentRobotic software on robots that can help doing repetitive, manipulative tasks (like carrying cargos) in industry.

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Communication applications (I)

for the purpose of communications on electronic media: Electronic Mail software: for creating,

sending and receiving, forwarding, storing, deleting or printing emails. (E.g., Microsoft Outlook)

Video conferencing software: for voice and video transmission

Instant Messaging software (such as ICQ): provides real-time communication among users.

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Communication applications (II)

for the purpose of communications on electronic media: Chat client software: for chatting online at

Internet Relay Chat/ Chat room. Web browser: used to access and view the

web pages. Electronic fund transfer (such as Automatic

Transfer Machine ATM). Other applications on Web: Revise the

Internet Services / Resources

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Multimedia applicationsDesktop Publishing: is software with sophisticated layout feature 排版 for publishing high-quality document such as marketing catalogs and annual report. E.g., Adobe PageMaker

http://www.adobe.com/products/pagemaker/overview1.html

Image Editing software (e.g. PhotoShop): editing graphics Video and Audio Editing software: for editing video or audio files.Web Page Authoring: for creating web pages

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EducationComputer aided learning: is a piece of interactive software to aid the learning of a particular subject (say, your English Oral Practice Software).Web-based learning (also known as E-learning): uses Internet technology for interactive and self-paced instructions on learning online.

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Other applications: Home

Embedded ( 內置 ) system: a computer system embedded in the processor of the product. In household appliances: e.g., A system emb

edded in the washing machine to control the washing stages.

Smart-house: A system (with artificial intelligence technology) installed in a house for controlling household activities

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Other applications: Artificial Intelligence

to create computers that imitate the human (brain) in Robotics: the technology of building and

using robots with artificial intelligence and computer controlled human-like capabilities.

Expert system: is the system of solving problems and giving advice in some knowledge-rich domain

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How to obtain software

2 Major approachesCustom-made software is designed and developed according to the part

icular client’s needs.

Application software ready-to-use software that is developed by soft

ware company to meet the general market needs.

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Custom-made software

is designed and developed according to the particular client’s needs. Advantages:

tailor-made to work effectively meeting the specific requirements.

may be able to change the software to accommodate the changing needs.

Disadvantages:It needs time and effort for the

software development.It is usually more costly for the initial

software development.

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Packaged software

ready-to-use software that is developed by software company to meet the general market needs. Advantages:

easy to get and install a package software relatively less costly as developed in mass

scale Are usually made to be user-friendly and to

provide support of service pack. Disadvantages:

lacks specificity and hence may not be suitable for different companies

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Installation of software (a)System requirements for system software: CPU speed requirement Hard disk storage requirement Other hardware requirement (e.g., enough size of

RAM)

System requirements for application software: CPU speed requirement Hard disk storage requirement Other hardware requirement (e.g., Modem installed

for the application software WinFax.) Compatibility with the Operating System

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Installation of software (b)Usually will be in the following ways:Complete installation: With all features installed. Unused features causes a waste of space.

Typical installation: with the usual features required installed. Specially required features may not be installed.

Custom installation: With chosen features by user installed. Users need to speed time to choose the features.