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System SoftwareSystem Software

• “Background software”, manages the computer’s internal resources

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System SoftwareSystem Software• Operating system

– Interface between application software (and user) and the computer

– Runs programs– Processes data– Stores information– Frees the user from complicated,

technical tasks

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Examples of Microcomputer Operating Examples of Microcomputer Operating System SoftwareSystem Software

•DOS - original standard for IBM compatibles

•Windows - a graphical operating environment

•Windows 95, Windows 98

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Examples of Microcomputer Operating Examples of Microcomputer Operating System SoftwareSystem Software

• Windows NT - for powerful workstations & networks

• OS/2 - competitor to Windows 95• Macintosh Operating System• Unix - originally for minicomputers,

now used on microcomputers and Internet servers

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Hardware - devices forHardware - devices for

•Input

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Hardware - devices forHardware - devices for

• Input

• Processing

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Hardware - devices forHardware - devices for

• Input• Processing

• Storage

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Hardware - devices forHardware - devices for

• Input• Processing• Storage• Output

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Hardware - devices forHardware - devices for

• Input• Processing• Storage• Output• Communications

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Input DevicesInput Devices• Translate data from form that

humans understand to one that the computer can work with

• Most common are keyboard and mouse

Selector Buttons

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The System UnitThe System Unit

•Electronic circuitry within the computer cabinet

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The System UnitThe System Unit• Two general parts

Central Processing Unit (CPU) - an integrated micro-circuit that translates data into information

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The CPU consists of :Control Unit (CU)Arithmetic and Logical Unit (ALU)

Some Registers.

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The Control Unit (CU) within a CPU coordinates all activities of the computer by determining which operations to perform and in what order to carry them out. The CU transmits coordinating control signals to other computer components.

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The ALU consists of electronic circuitry to perform arithmetic operations (addition, subtraction, multiplication and division), logical operations (and, or, not, …) and to make some comparisons (less-than, equal, … etc.)

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The System UnitThe System Unit

• Two general parts

•Memory - referred to as primary storage or random access memory (RAM), it temporarily holds data and programs for use during

processing (volatile)

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RAM

RAM consists of locations or cells. Each cell has a unique address which distinguishes it from other cells.

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ROM: Read Only Memory

ROM is part of memory.

Programmed at manufacturing time

Its contents cannot be changed by users

It is a permanent store

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Secondary StorageSecondary Storage• Stores data and programs

permanently: its retained after the power is turned off

• Located outside the CPU, but most often contained in the system cabinet

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Three Kinds of Disk DrivesThree Kinds of Disk Drives

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Common Secondary MediaCommon Secondary Media• Diskettes

– Data represented as magnetic spots on removable flexible plastic disks

– Most common size is 3 1/2 inches, in a rigid plastic case

– Disk drive holds the diskette, reads or retrieves the data and writes or stores data

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Common Secondary MediaCommon Secondary Media

• Hard drive– Data is represented magnetically as

with diskettes– Normally more than one rigid platter

in a sealed unit– These disks are not removable– Significantly more capacity and faster

operating than diskettes

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Output DevicesOutput Devices

Pieces of equipment that translate the processed information from the CPU into a form that humans can understand.

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Output Devices

MonitorsPrinters

Dot matrix printersInk jet printersLaser printers

Sound plasters

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Communications DevicesCommunications Devices

Hardware that sends and receives data and programs from one computer or secondary storage device to another.

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Units of Measurements

• Bit (Binary Digit)(takes two values: 1 or 0)

• Byte = 8 bits

• KB (Kilo-byte) = 1024 bytes

• MB (mega-byte) = 1024 KB

• GB (giga-byte) = 1024 MB

• TB (Tera-byte) = 1024 GB

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Data

Data are details of various types of transactions and details relating to specific situations, which are input to a data processing system (e.g. computer) for processing in a prescribed way. Examples of data relating to students are student-number, student-name and grades.

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DataData

• Document files

• Worksheet files

• Database files

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Information

Information: the result of processing data. Information:

Must serve a useful purpose Must be of an acceptable level of accuracy Must be available at the right time Must be relevant to the enterprise, person, … etc.

Knowledge

• Putting a number of information with the same type or same topic would be a knowledge.

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ConnectivityConnectivity

The computer’s capability to send and receive information from other locations.

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Systems of interconnected computers, known as networks, are the sources of distant information.

ConnectivityConnectivity

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Systems of interconnected computers, known as networks, are the sources of distant information.

The National Information Infrastructure (NII) is currently the Internet.

ConnectivityConnectivity

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Computer Viruses

A computer virus is an application program designed and written to destroy other programs.

- It has the ability to:Link itself to other programsCopy itself (it looks as if it repeats

itself)

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Examples of Viruses

MonkesABCCrabsCIH

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How do you know if you have a virus?

• Lack of storage capability

• Decrease in the speed of executing programs

• Unexpected error messages

• Halting the system

Protection against Computer Viruses

• Buy original copies of software only

• Make backups of your files

• Do not let any body to insert a diskette in your computer unless you are sure they do not have any viruses.

• Write-protect your disks

• Use anti-virus programs