3 computers and their components

Question 1

primary memory

Answer 1

• accessed directly from the cpu
• contains RAM and ROM
• temporarily stores data and instructions currently in use

Question 2

RAM

Answer 2

• can be written to and read from
• data stored can be changed
• volatile (contents are lost after powering off)

Question 3

dynamic RAM (DRAM)

Answer 3

• type of ram that needs to be constantly refreshed
• consists of transistors and capacitors
  advantages:
• less expensive than SRAM
• consume less power
• higher memory capacity

Question 4

Static RAM (SRAM)

Answer 4

-does not need to be consistently refreshed
-makes use of flip flops to hold each bit of memory
- faster data access time

Question 5

ROM

Answer 5

• can only be read from
• non volatile (contents are not lost after powering off)
• permanent memory devices (contexts cannot be changed)
• stores data that computer needs to access when powering up for the first time

Question 6

PROM

Answer 6

• programmable once only
• prom writer which uses an electric current to alter cells by burning fuses

Question 7

EPROM

Answer 7

-use floating gate transistors
- Can be erased by UV light and reprogrammed

Question 8

embedded system

Answer 8

small computers built into other devices

Question 9

advantage of embedded system

Answer 9

• small in size so easy to fit into devices
• low cost to make
• dedicated to one task

Question 10

disadvantages of embedded system

Answer 10

-difficult to upgrade
- limited functionality
- can be accessed over the internet so open to hackers

Question 11

secondary storage

Answer 11

-not directly accessible by the CPU
- non volatile devices
- device categories: magnetic, solid state, optical

Question 12

Hard disk drives (HDD)

Answer 12

• data is stored using magnetic patterns on spinning disks

Question 13

removable hard disk drives

Answer 13

-HDDS that are external to the computer connected by a USB port
- can be used as a backup device or another way of transfer files

Question 14

Solid state drives (SSD)

Answer 14

• has no moving parts and all data is retrieved at the same time
• store data by controlling movement of electrons within NAND chips
  sometimes use EEPROM
• use NOR chips
• faster but more expensive

Question 15

CDs and DVDS (optical storage)

Answer 15

-a red laser is used to read and write the data

Question 16

EEPROM

Answer 16

can be modified by the user, which can be erased and written to repeatedly using pulsed voltages

Question 17

DVD technology

Answer 17

dual layering which increases storage capacity
two individual recording layers

Question 18

Blu-ray discs (optical storage)

Answer 18

uses blue laser to carry out read write operations
stores more data than a DVD

Question 19

laser printer

Answer 19

use dry ink and use static electricity to produce the image

Question 20

inkjet printer

Answer 20

• a print head that sprays ink
• ink cartridge
• stepper motor and belt which moves the print head
• a paper feed which automatically feeds the printer with paper when they are required

Question 21

3D printer

Answer 21

produce working solid objects
built later by layer
direct 3D printing - print head can move left and right and up and down to build layers
binder 3D printing - first pass sprays dry power and second pass a binder is sprayed

Question 22

speaker

Answer 22

• data is passed through a digital to analogue converter where it is converted to an electric current
• then passed through an amplifier
• this current is fed to a loud speaker where it’s converted to sound

Question 23

microphone

Answer 23

• convert sound waves into digital signals
• diaphragm picks up air vibrations and starts to vibrate
• electrical signal is produced
• copper coil wrapped around a permanent magnet and connected to the diaphragm using a cone
• as the diaphragm vibrates the cone moves in and out
• this causes the magnetic field around the permanent magnet to be disturbed, inducing an electric current
  -electric current is amplified
  -

Question 24

screens capacitive

Answer 24

-made up of many layers of glass creating electric fields
- when top glass layer is touched, electric current changes and where the screen was touched is determined by an on board microprocessor
advantages
- medium cost
- good screen visibility
- durable
disadvantages
- only allows use of bare fingers as input

Question 25

screens resistive

Answer 25

- upper layer of polyester and bottom layer of glass - when top layer is touched it completes a circuit - signals are sent out which are interpreted by a microprocessor advantages - inexpensive - can use bare fingers, gloves or stylus disadvantages - poor screen visibility - screen wears out over time and scratches

Question 26

virtual headset

Answer 26

-video is sent from computer to headset - two feeds are sent to an LCD display - as the user moves their head, sensors measure their movement which allows the video to react to the users movement - use binaural sound - unse infrared sensors to monitor eye movement

Question 27

sensors

Answer 27

- sensors send signals to microprocessor - signals are converted to digital using ADC - microprocessor analyses the data by checking it against stored values

Question 28

monitoring system

Answer 28

collects data and does not change anything - if data is outside acceptable range, a warning message is sent or screen or alarm is activated

Question 29

control system

Answer 29

collects data and takes action - if the new data is outside the acceptable range, the microprocessor sends signals to control motor - system used feedback

Question 30

principal operations of a magnetic hard disk

Answer 30

- has one platter - platters are mounted on central spindle - entire mechanism is contained around a sealed aluminium box - disks are rotated at high speed - data is encoded as a magnetic pattern on each block