Computer Systems
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What do firewalls do?
Check data packets meet requirements , Protects against unauthorised access. Set rules about which stations on a network can send or receive packets
What rules do firewalls take account of?
Sender and receiver IP address, port numbers, protocols
What does encryption do?
Protects data during transmission Scrambles data so if stolen can’t understand Creates simple key that encrypts data Keeps simple key secure by combination of public and private keys
Public key?
Known by everyone, encrypts data
Private key?
Known by recipient, decypts data
what is a denial of service(DOS)
Floods website or online service so gets overloaded and stop working for real users
4 ways to reduce energy usage
Standby mode,hibernate mode,montior settings , power down settings
Standby mode?
• Ram contunies to be powered, • data temoray stored, • power to other components reduced or stopped
Hibernate mode?
Ram copied to harddisk, hard disk saves perment copy, all compoments off or very low energy use
Monitor Settings?
Reduce brightness, activate effeciency mode and don’t use screen saver
Power down settings?
Power down after a period of not using(Monitor,desktop/laptop), settings for indivual components
CPU(central processing unit)?
fetch, decode, excute instructions from RAM Preform arithmatic calculations & logical operations control, read, write,clock, inturrupt and reset lines(all wires)
What parts does the CPU consit of?
Control unit, ALU(ARithmatic and logic unit), registers
what does the control unit do?
manages the different lines
Clock line?
sends out signal to synochrise fetch&excute cycle
Read line?
read data from RAM
Write line?
writes data to RAM
Reset line
clears all registers
Intrrupt lines
handle interruptoions to a process during execution
ALU?
preforms all calculations, comparisons on numeric vaules, makes decisions based on logic (AND,OR,NOT)
Registers?
temorory storage locations in processor, stores addresses,data,instructions, fast access
Types of computer memory
different types with different purposes. Backing storage,main memory, cache,registers
Backing storage?
outside proccessor, stores data permently. e.g. usb memory stick
Main memory?
Inside computer, types- RAM(Random access memory), ROM (Read only memory)