Elements of a Computer System Dr Kathryn Merrick Thursday 4 th 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: 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

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, Software People, Procedures Main hardware components of a computer: Input Output Processing Storage