Elements of a Computer System

Dr Kathryn Merrick

Thursday 4th June, 2009

Overview

Elements of a computer system:

1. Hardware

2. Software

3. People

4. Procedures

1. Hardware Components

In order for a computer to do useful work it must have:

Input devices

Processing devices

Storage

Output devices

Mouse and Keyboard

Vision and Sound

Specialised Input Devices

Joystick

Wii

Force feedback steering wheel and pedals

Haptics devices

Central Processing Unit

Heart of Computer: Fetches program instructions

from memory Performs operation Writes result back into memory

Consists of a number of components

Registers where variables are stored

Arithmetic/Logic Unit (ALU)

Clock speed measured in GHz gives an indication of the power of the CPU

Graphics Processing Unit

Do computations related to 3D graphics 2D acceleration Frame buffering

At least as powerful as the CPU

Can be in video card or integrated directly into motherboard

Primary Storage

Memory is essential to store: The instructions of a program that is

executing The data upon which the program acts

Two main types: Random Access Memory (RAM) Read Only Memory (ROM)

Random Access Memory

Main memory of the computer

Small amount of fast memory used as a cache

Can be read from and written to

Volatile

When the power is turned off its contents are lost

Different speeds: faster is more expensive.

Read Only Memory

Cannot be written to by user

Non-volatile Burned in at time of

manufacture

Used to hold the boot code or bios code

Secondary Storage Equipment

Tape drive: used for archival storage up to 20 Gig (cheap and stable)

• CD: 600M capacity

• DVD: 5-9G Gig capacity

Flash memory capacity up to 32 Gig

Plug and play, quick and convenient

Old school floppies: storage in kB

Hard disk drive: 80-300 Gig capacity

Output Devices

Communication Devices

Computers need a way to communicate with other computers

Typical communication alternatives Local area network Wireless network Bluetooth

Infra-red

2. Software

Operating system software Manages system resources

Generic software Word processors, spread-sheets…

Specialised software Programming environments, 3D modelling,

organisation specific software…

Operating Systems

Manages sharing of system resources between processes Memory allocation Prioritising resource access Controls input and output Facilitates computer networking File system management

Provides programmers with an interface to access resources

Windows

OtherSolaris

MacLinux

June, 2008 Market Share

Windows 90.89%

Mac 7.94%

Linux 0.8%

Solaris 0.01%

Other 0.36%

3. People

Commercial computer systems often require a number of professionals to ensure the smooth running of the system:

System Administrator

Systems Analyst

Programmer

Systems Analyst

Help people and organisations solve their problems by identifying the role a computer system can play.

Identify what is possible and how a new system will work.

Gather system requirements

Develop models for a new system

System Administrator

Responsible for maintaining computer systems across an organisation:

Initial machine configuration

Creating user accounts

Granting network access

Fixing problems

4. Procedures

Hardware: how often are computers upgraded or replaced?

Application software: when are new versions purchased?

Backup routine: how often? where are copies kept?

Anti-virus software: how is is renewed?

Security: who has access to servers?

Passwords: how many letters / numbers?

Summary

After this lecture you should be able to describe and give examples of:

Elements of a computer system:Hardware, SoftwarePeople, Procedures

Main hardware components of a computer: InputOutputProcessingStorage