computer systems

computer systems

1. components of a computer system

2. data representation

3. networks

   • types of network
     • LANs - local area networks
       • LANs cover a small geographical area. LAN hardware is usually owned by the organisation using it.
       • Users on a LAN can:
         • access and share files on the network
         • share hardware
         • share an internet connection
         • log in from any device on the network
         • roll out security and software updates to all computers at once
     • WANs - wide area networks
       • WANs connect LANs in different geographical locations.
       • Organisations hire infrastructure from telecommunications companies, who own and manage the WAN.
       • more expensive to set up than LANs
     • network performance
       • BANDWIDTH - amount of data that can be transferred in a given time. It's shared between devices on a network.
       • wired performance can depend on the types of cables used
       • wireless performance depends on signal quality, which is affected by: range of the device; interference from other networks; physical obstructions
   • network hardware
     • Network Interface Controller
       • Allows devices to connect to a network - usually built into the motherboard
     • Switch
       • Receives and transmits data between devices on a LAN using MAC addresses
     • Transmission Media
       • Wired or wireless radio waves that allow data transmission between devices
     • Wireless Access Point
       • Allows devices to connect to a network wirelessly. SImilar to a switch.
     • Router
       • Transmits data between networks by directing data as packets to their destination
     • wired networks
       • three cables to connect devices on an Ethernet (wired) network:
         • twisted pair
           • copper wires twisted together in pairs to reduce internal interference
         • coaxial
           • a single copper wire surrounded by plastic insulation and metallic mesh to shield from outside interference
         • fibre optic
           • transmits data as light. can send data over long distances with little interference. high performance but expensive
     • wireless networks
       • radio waves transmit data between devices on wireless networks
       • two common wireless technologies:
         • bluetooth
           • direct connection between two devices to share data. low bandwidth. max range 10 metres
         • Wi-Fi
           • can connect multiple devices to a LAN at once. high bandwidth. max range 40 - 100 metres

4. issues