topic 4: computers

input

to enter data into a computer

process

to change the meaning or format of some data

output

to display or output data that has been processed

sequential

following instructions in an algorithm step by step in order from start to finish

parallel

process is distributed between two or more processors installed

multi agent

separate tasks are processed by different agents

RAM

can be read from and written to

fast access

the operating system

software in use

the data the software is using

virtual memory

a part of the hard drive and used as an extension of ram

von neumann architecture

computer system designed in which the program is stored in memory with the data

cache

memory used to make up for the difference in speeds between two internal components

the cpu

executes programs and manages the rest of the hardware

control unit

controls the execution of instructions in the correct sequence

it decodes instructions

it regulates and controls processor timing using regular pulses from the system clock

it sends and receives control signals to and from other devices within the computer

ALU

performs arithmetic operations and logical operations

fetch decode execute

fetch - causes the next instruction and any data involved to be fetched from main memory

decode - decodes the instruction

execute - carries out the instruction

program counter

contains the address of the next instruction tot be fetched

address bus

unidirectional and carries the address to a desired location in the main memory

data bus

the data in the location is returned to the CPU

control bus

control signals are transported

clock speed

faster clock speed, faster rate of processing

however, the processor generates a large amount of heat which increases as the clock speed increases

factors that affect cpu performance

clock speed

number of processor cores

size of cache

magnetic

mechanical parts move over the disks surface to read and write data magnetically

optical

data is stored as pits and lands and a laser beam passes over the pits and lands

solid state

data is recorded onto solid memory chips without any moving parts

magnetic advantages

cheap

cast storage capability

fast write speed

magnetic disadvantages

lots of mechanical parts

durability is an issue

not very portable

optical advantages

cheap

very portable

takes up little space physically

optical disadvantages

less storage capacity compared to other types

easily damaged

requires a reader

slow write speeds

ssd advantages

highly durable

no moving parts

very fat read/write speeds

no noisy fan

faster start up times

ssd disadvantages

expensive at present

less storage capacity than traditional hsrd disk

cloud storage

saving data in an offsite storage system maintained by a third party

cloud computing advantages

able to access data and applications anytime from anywhere

no need for a powerful computer with a huge hard drive

backing up data is no longer needed

cloud computing disadvantages

handing over important data to other companies may worry people

sensitive data can be more vulnerable to hacking

truth table

a table showing all possible combinations of the inputs and outputs of an operator

functions of an operating system

provides user interface

manages memory, multitasking, peripherals, files and user access rights

different UIs

GUI

menu driven

CLI

voice activated

interrupts

signals sent to the cpu by external devices to indicate and event that needs immediate attention

embedded systems

a dedicated computer system designed to perform a few specific functions

security utilities

anti virus

spyware protection

firewalls

backup and recovery

firewall

prevents unauthorised access to a computer or network from the internet

disk defrag

moves separate parts of the files around so that they can be stored together