3 - hardware

Question 1

primary memory

Answer 1

can be accessed directly from the CPU

Question 2

RAM

Answer 2

Random Access memory
- can be written to and read from
- stores files/ data currently in use
- volatile (memory contents are lost powering off the comp)
- can increase size to improve operational speed

Question 3

ROM

Answer 3

• non volatile
• permanent memory (can’t change contents)
• stores data the comp uses when powering up (BIOS/ bootstrap)

Question 4

DRAM

Answer 4

dynamic RAM
- capacitors hold the bits of information
- transistors act like switches and allow chip to control circuit to read/ write the capacitor
- needs to be refreshed constantly - if not charge will leak away leaving it with 0
+ cheaper
+ consume less power
+ higher memory capacity
used by main memory

Question 5

SRAM

Answer 5

uses flip flops which hold each bit
+ doesn’t need to be refresehd
+ faster
- if accessed at a high freq power usage can exceed a DRAM
memory cache generally uses SRAM for this reason

Question 6

PROM - Programmable ROM

Answer 6

• can be altered once
• made of a matrix of fuses
• uses electric current - burns fuses to alter specific cells
  eg mobile phones, RFID tags

Question 7

EPROM - Erasable Programmable ROM

Answer 7

• use floating gate transistors and capacitors not fuses
• UV light programs it through a quartz window
  eg new games consoles, apps under development

Question 8

EEPROM -electrically erasable programmable ROM

Answer 8

• electrical signal can be used to remove existing data
  + chip can remain in the circuit while contents are changed

Question 9

buffers

Answer 9

• ## temporary storage for data transmitted from one part of the system to another which functions as a queue

Question 10

embedded systems +

Answer 10

+ small so easy to fit
+ low cost
+ dedicated to one task - simple interface - no OS
+ consume little power
+ very fast reaction to changing input
+ mass production so reliable

Question 11

embedded systems -

Answer 11

• difficult to upgrade devices - with new tech
• fixing it is specialist
• interface can be simple but in reality it can be confusing
• open to hackers and viruses
• due to difficulty in upgrading and fixing devices are throw away - wasted

Question 12

embedded system

Answer 12

A computer system with one dedicated task ( no multitasking)
hard for the user to update
built in hardware and software

Question 13

magnetic storage - HDD

Answer 13

• has platters - that spin
• has read/write arm
• data stored on surface in sectors and tracks
• magnetic field determines binary value

Question 14

latency

Answer 14

time it takes for a specific block of data on a data track to rotate around to the read-write head

Question 15

removable hard disk drives

Answer 15

are HDDs that are external to the comp and can be connected to the comp using a USB port

Question 16

magnetic storage +/-

Answer 16

+ large storage
+ cheap
+ fast read/write
- lots of parts
- not durable
- sealed unit ( cant fix easily)
- not portable

Question 17

solid state storage - SSD

Answer 17

• sends current which forces electrons through a barrier
• and traps them in floating gates
• binary data is stored by the held electrons
  (flash memory)

Question 18

SSD +/-

Answer 18

+ reliable - no moving parts
+ lighter
+ less power consumption
+ run cooler than HDDs
+ access data faster
- expensive
- unknown longevity

Question 19

optical storage - CD DVD

Answer 19

• is a disk - with a spiral track
• binary represtented using pits/lands
• laser shines on - pits reflect light differently to determine binary value (read)
• laser makes indents on disk (write)

Question 20

dual layering

Answer 20

used in DVDs to increase storage capacity
2 layers which are joined together
- shorter the wavelength of laser light the greater the storage capacity of the medium
- can cause birefringence (light is refracted into two beams causing reading errors)

Question 21

blu-ray

Answer 21

• uses blue laser (shorter wavelength)
• blue light means pits and bumps can be much smaller (can store more)
• uses a single thicker disk - no birefringence
• automatically come with encryption

Question 22

laser printers

Answer 22

• use dry powder ink and static electricity
• ## use blue cyan magenta black - print all in one go

Question 23

inkjet printers

Answer 23

• nozzles spray ink onto paper
• has a stepper motor and belt which moves the print head across the page
• a paper feed which feeds the printer with pages as required
• thermal bubble of piezoelectric

Question 24

thermal bubble

Answer 24

• tiny resistors create localised heat which makes the ink vaporise
• causes the ink to form a tiny bubble, as the bubble expands some of the ink is ejected from the print head onto the paper
• when the bubble collapses, a small vacuum is created which allows fresh ink to be drawn into the print head
• this continues until the printing cycle is completed.

Question 25

piezoelectric

Answer 25

– a crystal is located at the back of the ink reservoir for each nozzle - The crystal is given a tiny electric charge which makes it vibrate - This vibration forces ink to be ejected onto the paper and at the same time more ink is drawn in for further printing.

Question 26

3D printers

Answer 26

-solid object is built up using resin, metal or ceramic

Question 27

speakers

Answer 27

- passed through DAC - passed through amplifier to create larger current - electric current is then fed to speaker - current fed into wire - wire wrapped round core - interacts with magnet - vibrates creating sound waves

Question 28

microphones

Answer 28

- diaphragm in the mic vibrates - coil is wrapped around magnet - coil is connected to the diaphragm using a cone - cone moves in and out causing the copper coil to move backwards and forwards. - causes the magnetic field around the permanent magnet to be disturbed, inducing an electric current. - current is then either amplified or sent to a recording device

Question 29

keyboard

Answer 29

- allows test input - key press converted into character code - transmitted to a processor - processor displays character on screen

Question 30

screens

Answer 30

- use LCD backlit with LED or OLED (organic light emitting diode) - OLED - give off light when electricity applied to electrodes - each screen pixels is made up of 3 sub pixels RGB

Question 31

capacitive touchscreens

Answer 31

- made up of layers of glass acting as a capacitor creating electric fields between glass layers - When the top layer is touched, the current changes - location is calculated by microprocessor + medium cost + good visibility + multi touch + durable - only allows bare fingers

Question 32

resistive touchscreens

Answer 32

- makes use of upper and bottom layer - when touched layers touch making complete circuit - signals are sent out which are interpreted by microprocessor + cheap + can use any touch - bare, gloved fingers - poor visibility - no multi touch - not durable

Question 33

virtual headsets

Answer 33

- video sent from a comp to headset - two feeds are sent to an LCD/OLED - one for left and right - lenses reshape video making it 3D - when user moves head sensors measure movement - use binaural sound (surround sound - some use infrared sensors to monitor eye movement

Question 34

sensors

Answer 34

- are input devices which read or measure physical properties such as temp pressure acidity etc. - uses ADC - converts physical values into digital values - microprocessor analyses data - if outside acceptable range alarm is raised or signals sent to control valves

Question 35

anti-lock braking system

Answer 35

use magnetic field sensors to stop the wheels locking if they have been applied too sharply - when one of the car wheels rotates too slowly data is sent to microprocessor - checks rotation of other wheels - changes it to match others - constantly being checked to prevent locking

Question 36

latency

Answer 36

lag in a system egg time to find track on a disk

Question 37

flash memory

Answer 37

a type of EEPROM suited to use in SSDs

Question 38

logic gate

Answer 38

take binary inputs and produce an output

Question 39

logic circuit

Answer 39

several logic gates combined for a specific function

Question 40

NOT

Answer 40

triangle shape if A is TRUE- X is NOT TRUE X = NOT A X = A ̅

Question 41

AND

Answer 41

D shape if A is TRUE and B is TRUE - X is TRUE X = A AND B X = A.B

Question 42

OR

Answer 42

)D shape if A is TRUE OR B is TRUE - X is TRUE X = A OR B X = A + B

Question 43

NAND

Answer 43

Dº shape is A is NOT T or B is NOT T - X is T X = A NAND B X = ̅A.B ̅

Question 44

NOR

Answer 44

)Dº shape if A is NOT T and B is NOT T - X is T X = A NOR B X = ̅A+B ̅ ̅ ̅

Question 45

XOR

Answer 45

))D shape X= 1 if (A is 1 AND B is NOT 1) OR (A is NOT 1 AND B is 1) X = A XOR B X = A ⊕ B

Question 46

truth table

Answer 46

trace the output from a logic circuit all possible input combinations are considered