Computer Systems - PowerPoint PPT Presentation

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Computer Systems can be viewed as a set of five cooperating subsystems: ... Tells the computer how to perform operations like input, output and storage ...

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Computer Systems

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Computer Systems

  • A computer system is a combination of hardware and software , functioning together, processing data to achieve a purpose.

  • Computer Systems can be viewed as a set of five cooperating subsystems:


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Computer Systems

  • A computer is an electronic device that accepts inputs, processes them and produces an output.

  • In processing, the computer follows out instructions

  • To carry out the instructions the following are needed:

    • Hardware

    • Software

    • Data

    • People

    • Procedures

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  • Software is a set of instructions that direct the hardware to perform certain tasks.

  • There are 3 types of software :

  • Systems Software

  • Utility Software

  • Applications Software

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Systems/Operating Software

  • Tells the computer how to perform operations like input, output and storage

  • Operating system-collection of programs used to organise files, communicate with peripheral devices and assist in the operation of the computer

  • The link between hardware and application software ( eg DOS, WINDOWS (95/98, XP)

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Utility Software

  • Specialised programs that perform 1 or a few basic tasks

  • Examples are virus checkers, spell checkers, clock , calculator,editors etc

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Applications Software

  • Designed to carry out a particular task, or to solve a user’s problem

  • allows computer to perform a wide range of tasks

  • Examples: Word processing packages

  • Spreadsheet packages ( E.g Excel)

  • Games

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  • INPUT –involves entering data into the computer.

  • This is a signal sent to the computer usually from the keyboard or mouse

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  • OUTPUT-involves the display of information to a person, data or another computer.

  • A signal sent from the computer to an attached device.

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  • STORAGE –involves the saving of a signal or a set of signals on a convenient medium

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  • PROCESS- carrying out a set of instructions, which occurs in the CPU. Changes data to produce information

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  • CONTROL –co ordinates the operations of the above.

  • Control is part of the CPU. It directs flow.

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  • This is the machinery that makes up a computer system – the parts you can touch.

  • Hardware is classified into Peripheral Devices and Central Processor Devices

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Peripheral Devices

  • Peripherals are anything that you attach to a computer

  • These are associated with input, output and storage.

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Input/Output Devices

  • Interface between a system and its environment

  • They are classified according to speed, flexibility, convenience and cost

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most common - QWERTY keyboard



digitising - views a page and produces an image

flatbed and hand held

Other Devices

digital camera

video camera

graphics tablet

light pen

barcode reader

temperature sensor

voice recognition equipment



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Inkjet/Bubble jet



also called VDU - visual display unit

display broken into a grid of pixels

Laptops have a flat panel - LCD - liquid crystal display

Other output devices



sound card


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The Central Processing Unit (CPU)

  • All processing takes place here

  • CPU is made up of millions of electrical circuits put into a silicon chip or integrated circuit

  • CPU is situated on the motherboard

  • CPU is measured in Megahertz(Mhz)

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Structure of CPU

  • CPU is made of 3 parts

  • Arithmetic Logic Unit (ALU) – performs arithmetic (=,-,x./) or logical operations on data. “Logical” includes comparing 2 items.

  • Registers –temporary storage locations for data currently being processed by the CPU

  • Control Unit – directs the flow of data and program instructions within the computer system. It controls movements of data between input, output, ALU and storage

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  • Buses – data travels throughout the motherboard on bus lines

  • Bus lines are soldered wire and appear silver.

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  • People who work in the computer industry can be categorised as follows:

  • Design and Construction

  • Operations and Management

  • Users

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Design and Construction

  • These people plan and develop new computer systems or modify old systems.They include:

    • Systems analyst

    • Programmers

    • Engineers

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Operations and Maintenance

  • They keep the system working efficiently so that it achieves its purpose. They include:

    • Managers

    • Computer Operators

    • Data entry

    • Consultants

    • Technical support

    • Computer technicians

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  • Users are people who are affected by computer systems. They include:

    • Direct Users

    • Indirect Users

    • Intermediary Users

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