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AS Computer Science > Chapter 3 - Hardware > Flashcards

Chapter 3 - Hardware Flashcards

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1
Q

Memory cache

A

High speed memory external to processor which stores data which the processor will need again

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2
Q

RAM

A

Random Access Memory
Primary memory unit that can be read to and written from

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3
Q

ROM

A

Read Only Memory
Primary memory unit that can only be read from

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4
Q

DRAM

A

Dynamic Read Only Memory
Type of RAM chip consisting of transistors and capacitors that needs to be constantly refreshed, meaning the capacitance needs to be be recharged every 15 microseconds to prevent charge leaking away leaving every capacitor with the value of 1

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5
Q

SRAM

A

Static Read Only Memory
Type of chip that uses flip-flops and does not need refreshing and has a faster data access time than DRAM

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6
Q

Refreshed

A

Requirement to charge a component to retain its electronic state

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7
Q

PROM

A

Programmable Read Only Memory
Type of ROM chip that can be programmed once. Made up of a matrix of fuses. To program you need a PROM writer which uses an electric current to alter specific cells by burning fuses in the matrix. Often used in mobile phones and RFID tags

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8
Q

EPROM

A

Erasable Programmable Read Only Memory
Type of ROM that can be programmed more than once using UV light

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9
Q

HDD

A

Hard Disk Drive
Type of magnetic storage that uses spinning disks (platters). There are a number of platters (doubled sided) which spin around 7000 times a second allowing a number of read-write heads (that move very quickly) to access all surfaces in the disk drive. They are typically able to move from the centre of the disk to the edge and back 50 times a second. Data is stored on sectors and tracks which contain a fixed no. Of bites.

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10
Q

Latency

A

The lag in a system
Eg. Time to find a track on a hard disk, which depends on the time taken for the disk to rotate around its read-write head

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11
Q

Fragmented

A

Storage of data in non-consecutive sectors
Eg. Due to editing + deletion of old data (basically messily stored)

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12
Q

Removable hard disk drive

A

Portable hard disk drive that is external to the computer, can be connected via a USB port when required; often used as a device to back up files and data

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13
Q

SSD

A

Solid State Drive
Storage media with no moving parts that relies on movement of electrons

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14
Q

EEPROM

A

Electrically Erasable Programmable Read Only Memory
ROM chip that can be modified by the user which can then be erased + written to repeatedly using pulsed voltages. Uses floating gate transistors and capacitors. Programmed using UV light through a quarts window and used in applications under development (programming consoles)

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15
Q

Flash memory

A

Type of EEPROM
Particularly suited to use in drives such as SSDs, memory cards and memory sticks

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16
Q

Optical storage

A

CDs, DVDs and Blu-ray Discs that use laser light to read and write data

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17
Q

Dual layering

A

Used in DVDs; uses 2 recording layers of standard DVD joined together with a polycarbonate spacer with a very thin reflector sandwiched between the layers. Reading + writing of the second layer is done by a red laser focusing at a fraction of a millimetre compared to the first layer

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18
Q

Birefringence

A

A reading problem with DVDs caused by refraction of laser light into 2 beams

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19
Q

Binder 3D printing

A

3D printing method that uses a 2 stage pass. First stage uses dry powder, second uses a binding agent

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20
Q

Direct 3D printing

A

3D printing technique where print head moves in the x,y and z directions. Layers of melted material are built up using nozzles like an inkjet printer

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21
Q

Direct 3D printing

A

3D printing technique where print head moves in the x,y and z directions. Layers of melted material are built up using nozzles like an inkjet printer

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22
Q

DAC

A

Digital to Analogue Converter
Needed to convert digital data into electric currents that can drive motors, actuators and relays for example

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23
Q

ADC

A

Analogue to Digital Converter
Needed to convert analogue data into a form understood by a computer

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24
Q

OLED

A

Organic Light Emitting Diode, self contained system
Uses organic materials (organic compounds) to create flexible semiconductors. Organic films are sandwiched between 2 charged electrodes (one metallic anode and one glass anode). Light is given off when an electric current is applied to one of the electrodes, so no back lighting required.
Uses movement of electrons between cathode and anode to produce an on-screen image.

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25
Q

Screen resolution

A

Number of pixels in the horizontal + vertical directions on a television/computer screen

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26
Q

Touch screen

A

Screen on which the touch of a finger/stylus allows selection/manipulation of a screen image. Usually use capacitive or resistive technology

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27
Q

Capacitive

A

Type of touch screen technology based on glass layers forming a capacitor where fingers touching the screen causes a change in the electric field

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28
Q

Resistive

A

Type of touch screen technology. When a finger touches the screen, the glass layer touches the plastic layer, completing the circuit and causing a current to flow at that point.

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29
Q

Virtual reality headset

A

Apparatus worn on the head that covers the eyes like a pair of goggles. Immerses the user totally in the virtual reality experience

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30
Q

Sensor

A

Input device that reads physical data from its surroundings

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31
Q

Memory

A

Internal devices which the computer can access directly

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32
Q

Primary memory

A

Part of computers memory which can be accessed directly from the CPU. Contains RAM and ROM memory chips. Allows the processor to access applications and services temporarily stored in memory locations

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33
Q

Secondary storage (3)

A

HDD
SSD
Removable devices
-DVD/CD/Blu-ray
-HDD (removable)

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34
Q

Structure of primary memory (diagram)

A
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35
Q

Features of RAM (3)

A

Can be read to/written from and stored data can be changed by the user/computer
Used to store data, files or other things currently in use
Volatile

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36
Q

When does RAM become full

A

When the processor has to continually access secondary data storage to overwrite old data on RAM with new data. Increasing RAM size will reduce the number of times this must be done making it operate faster

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37
Q

Types of RAM technology (2)

A

DRAM (dynamic)
SRAM (static)

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38
Q

Capacitors on a DRAM

A

Hold bits of information (0 or 1)

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39
Q

Transistors on a DRAM

A

Act like switches, allow the chip control circuitry to read the capacitor or change the capacitors value

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40
Q

Advantages of DRAM over SRAM (3)

A

Less expensive to manufacture
Consumer less power
Higher memory capacity

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41
Q

What is main memory constructed from

A

DRAM

42
Q

Power usage of SRAM vs DRAM

A

DRAM consumes more power under reasonable levels of access since it needs to be constantly refreshed
SRAM can exceed DRAM power usage if accessed at a high frequency

43
Q

Power usage of SRAM vs DRAM

A

DRAM consumes more power under reasonable levels of access since it needs to be constantly refreshed
SRAM can exceed DRAM power usage if accessed at a high frequency

44
Q

Where would SRAMs be used

A

Where absolute speed is essential, such as the memory cache.

45
Q

RAM (5) vs ROM (4)

A

RAM
-Temporary memory device
-Volatile
-Can be read to + written from
-Used to store files, programs etc currently in use
-Size can be increased to improve operational speed of a computer
ROM
-Permanent memory device
Non volatile
Stored data cannot be altered
Sometimes used to store BIOS + other start up data

46
Q

Embedded systems

A

Microprocessors installed into devices to enable operations to be controlled more efficiently

47
Q

Pros of embedded systems (6)

A

Small in size (fit easily into devices)
Relatively low cost to make
Simple interfaces so no need for an OS (only perform one task)
Consumer very little power
Very fast reaction to changing input (operate in real
Mass production means reliability

48
Q

Cons of embedded systems (5)

A

Difficult to upgrade
Troubleshooting faults become a specialist task
Interface can be confusing
Open to hackers/viruses if it can access the Internet
Wasteful since devices are often thrown away instead of repaired

49
Q

Disadvantages of HDD

A

Slow data access compared to RAM and run the risk of becoming fragmented. Latency becomes a large issue

50
Q

How SSDs store and retrieve data

A

They have no moving parts and all data is retrieved at the same rate. Data is stored by controlling the movement of electrons within NAND chips. Data is 0s and 1s in millions of tiny transistors (each corner one is floating and the other is control gate) within the chip. Non-volatile memory produced

51
Q

EEPROM vs SSD

A

NOR vs NAND

52
Q

Benefits of using SSD rather than HDD (7)

A

More reliable (no moving parts)
Considerably lighter (suitable for laptops)
Don’t need to speed up before working properly
Lower power consumption
Run cooler (make them suitable for laptops)
Very thin (no moving parts)
Access data considerably faster

53
Q

Drawback of SSD

A

Unknown longevity
Most are rated at 20GB write operations per day over 3 year period (SSD endurance). Can thus not be used in servers where a higher number of write operations take place daily

54
Q

Use of a dongle

A

In complex/expensive software such as an expert system. Memory stick used as a dongle which contains additional files needed to run the software. Prevents illegal use or copying of software since it is useless without the dongle

55
Q

CDs and DVDs

A

Store data in pits and bumps on a single, spiral track on a thin layer of metal alloy or light-sensitive organic material. When the disk spins the optical head moves to the point where the laser contacts the disk surface and follows the track from the centre outwards. Divided into tracks and the outside runs faster than the inside. Can be designated Read or Read and Write

56
Q

CD vs DVD

A

Single layer vs. Dual layered
Single layer DVD still has larger storage capacity since the pit size and track width are both smaller
Wavelength of 780nm vs 650nm

57
Q

Affect of wavelength of laser light on storage capacity of the medium

A

Shorter the wavelength the greater the capacity

58
Q

Blu-ray vs DVD (6)

A

Both optical storage media, carry out read-write operations differently
Use blue lasers(405nm) instead of red (650)
Pits and bumps are much smaller allowing 5 times the storage capacity
Uses single 1.1mm polycarbonate disk compared to a sandwich of 2 0.6mm disks
Does not suffer from Birefringence since it only has 1 layer
Automatically come with a secure encryption system which prevents piracy + copyright issues

59
Q

Laser colour + wavelength of
CD
DVD
Blu-ray

A

Red - 780 nm
Red - 650nm
Blue - 405nm

60
Q

Disk construction + track pitch (distance between tracks)
CD
DVD
Blu-ray

A

1 1.2mm polycarbonate layer - 1.6 μm
2 0.6mm polycarbonate layers- 0.74 μm
1 1.1mm polycarbonate layer - 0.3 μm

61
Q

Laser printers

A

Use dry powder ink and static electricity to produce text and images. Print the whole page in one go with 4 toner cartridges (blue, cyan, magenta, black0

62
Q

Printing using a laser printer (11)

A

-Data sent to printer driver
-Driver ensures the data is in the correct format
-Driver checks if the printer is able to+ready to print
-Data sent to printer and stored in the buffer
-Printing drum is given a positive charge, rotates and w laser beam removes the charge in certain areas to match the text/image of the page to be printed
-Drum is coated in positively charged toner which only sticks to the negatively charged parts
-Negatively charged paper is rolled over the drum
-Toner sticks to the paper to produce an exact copy
-Electric charge on the paper is removed after 1 rotation to prevent sticking
-Paper goes through a fuser to melt the ink and permanently fix it to the paper
-Discharge lamp removes all the charge from the drum

63
Q

Inkjet printer components (4)

A

Print head consisting of nozzles that spray droplets of ink onto the page
Ink cartridge/s (one cartridge for each colour + black or one single cartridge for all 6 colours)
Stepper motor + belt to move the print head assembly side to side
Paper feed to automatically feed the printer pages as required

64
Q

Ink jet technologies (2)

A

Thermal bubble
Piezoelectric

65
Q

Thermal bubble inkjet technology

A

Tiny resistors create localised heat which vaporises the ink causing it to form a tiny bubble. As the bubble expands some of the ink is ejected from the print head onto this paper. Once 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

66
Q

Piezoelectric inkjet technology

A

Crystals located at the back of the ink reservoir for each nozzle are given a tiny electric charge and start vibrating which forces ink to be ejected onto the paper whilst simultaneously drawing in more.

67
Q

Steps in ink jet printing (9)

A

-Data sent to printer driver
-Driver ensures the data is in the correct format
-Driver checks if the printer is able to+ready to print
-Data sent to printer and stored in the buffer
-Sheet of paper fed into main body and is detected by a sensor (error message sent if absent)
-As it is fed the print head moves across the paper spraying the colours in exact amounts
-At the end of each full pass the paper is advanced to print the next row (continued until done)
-If there is more data in the buffer, the process repeats until it’s empty
-Once the buffer is empty the printer sends an interrupt to the processor in the computer to request more data and the process repeats until the document is printed

68
Q

3D printers

A

Used to produce working, solid objects primarily based on inkjet

69
Q

Function of virtual reality headsets (7)

A

Video sent from a computer to headset using HDMI cable/smartphone fitted into headset
2 feeds sent to an LCD/OLED display, lenses placed between eyes allow for focusing +reshaping of the image for each eye (3D)
Most have 110* field of view to give a pseudo 360* surround image/video
Frame rate of 60 to 120 images per second use to give a realistic image
Series of monitors/LEDs (usually gyroscopic/accelerometers) measure head movement so that the video can react realistically
Use binaural sound (surround sound) to give a realistic 3D sound
Some use infrared sensors to monitor eye movement allowing the depth of field on screen to be more realistic

70
Q

Actuator

A

Electromechanical device such as a relay, solenoid or motor

71
Q

Example applications of temperature sensor (3)

A

Control central heating system
Control/monitor a chemical process
Control/monitor temperature in a greenhouse

72
Q

Example applications of moisture/humidity sensor (2)

A

Control/monitor moisture/humidity levels in soil/air in a greenhouse
Monitor dampness levels in an industrial application

73
Q

Example applications of light sensors (3)

A

Switch lighting on/off depending on the time
Monitor/control light levels in a greenhouse
Switch on car headlights when it gets dark

74
Q

Example applications of infrared/motion sensors (3)

A

Turn on windscreen wipers on a car when it rains
Detect an intruder in a burglar alarm system
Count people entering/leaving a building

75
Q

Example applications of pressure sensors (3)

A

Detect an intruder in a burglar alarm system
Check weight
Monitor/control a process where gas pressure is important

76
Q

Example applications of acoustic/sound sensors (2)

A

Pick up noise levels in a burglar system
Detect noise of liquid dripping from a pipe

77
Q

Example applications of gas sensors (3)

A

Monitor pollution levels
Mesure O2 and CO2 levels in a greenhouse
Check for gas leaks in a power station

78
Q

Example applications of pH sensors (2)

A

Monitor/control acidity/alkalinity levels in soil
Monitor pollution in rivers

79
Q

Example applications of magnetic field sensors (2)

A

Detect changes in cell phones, CD players etc
Used in antilock braking systems,s in motor vehicles

80
Q

Monitoring system (5)

A

Sensors send signals to the microprocessor/computer
Signals converted to digital using an ADC
Microprocessor/computer analyses data received by checking it against stored values
If new data is outside the acceptable range, a warning message is sent to a screen or an alarm is activated
Has no effect on what is being monitored, it simply watches

81
Q

Control system (5)

A

Sensors send signals to the microprocessor/computer
Signals converted to digital using an ADC
Microprocessor/computer analyses data received by checking it against stored values
If the new data is outside the acceptable range, the microprocessor/computer sends signals to control valves and motors etc.
Output from the system affects the next set of inputs from the sensors

82
Q

Examples of monitoring (4)

A

Monitoring vital signs of hospital patients
Checking for intruders in a burglar alarm system
Checking temperature levels in a car engine
Monitoring pollution levels in a river

83
Q

Examples of control (3)

A

Turning on street lights at night/on at day
Controlling temperature in a central heating/cooling system
Controlling the traffic lights at a road junction
Operating anti-lock brakes on a car
Controlling the environment in a greenhouse

84
Q

What are anti lock braking systems

A

Use magnetic field sensors to stop the wheels locking up on the car if the brakes have been applied too sharply

85
Q

Function of antilock braking system on cars (7)

A

When one wheel rotates too slowly a magnetic field sensor sends data to a microprocessor
Microprocessor checks rotation speed of the other 3 wheels
If they are different the microprocessor sends a signal to the braking system and the pressure on the wheel is reduced
The rotational speed is then increased to match the other wheels
The checking is done several times a second and the braking pressure is constantly changing to avoid wheels locking
This is felt as a judder on the brake pedal as the system constantly switches on + off to equalise the rotational speed
If one wheel is too quick the braking pressure is increased

86
Q

Binder 3D printing

A

Similar to direct 3D printing, but uses 2 passes for each of the layers, the first spraying a dry powder and then a binder
Newer technologies use lasers +UV to harden liquid polymers

87
Q

Digitised sound stored in a file on a computer converted into sound (3)

A

Digital file is first passed through a DAC to convert it to an electric current
It is then passed through an amplifier to create a current loud enough to drive a loudspeaker
The electric current is then fed to a loudspeaker where it is converted to sound

88
Q

Digitised sound stored in a file on a computer converted into sound (3)

A

Digital file is first passed through a DAC to convert it to an electric current
It is then passed through an amplifier to create a current loud enough to drive a loudspeaker
The electric current is then fed to a loudspeaker where it is converted to sound

89
Q

Functioning of a loudspeaker (3)

A

-Electric current flows through a coil of wire wrapped around an iron core, causing the core to become a temporary electromagnet.
-As the electric current through the coil varies, the induced magnetic field varies causing the iron core to be attracted to the permanent magnet causing the core to vibrate
-This causes the attached cone (made from paper/thin synthetic material) to vibrate + produce sound

90
Q

Workings of a microphone (5)

A

-Sound causes air to vibrate
-Diaphragm in the microphone picks up the vibrations and also begins to vibrate
-Copper coil is wrapped around a permanent magnet and connected to the diaphragm using a cone which moves in and out as the diaphragm vibrates causing the coil to move back+forth
-Motion disturbs the magnetic field around permanent magnet, inducing an electric current
-Current (analogue in nature) is then either amplified or sent to a recording device

91
Q

Pixel concept

A

Each screen pixel is made up of 3 sub-pixels (RGB), by varying the intensity of the sub-pixels, it is possible to generate millions of colours

92
Q

Capacitive screen (2)

A

-Made up of tiny layers of glass that act like a capacitor creating electric fields between the glass plates in layers
-When the top glass layer is touched the electric current changes + the coordinates where the screen is touched are determined by an on board microprocessor

93
Q

Benefits capacitive screens (4)

A

Medium cost technology
Screen visibility is good in strong sunlight
Multi-touch capacity
Screen very durable

94
Q

Capacitive screen drawback

A

Only allows use of bare fingers as form of input (latest screen allows a special stylus)

95
Q

Resistive screen (3)

A

Makes use of an upper layer of polyester and a bottom layer of glass
When the top layer is touched the 2 layers complete a circuit
Signals are sent out + interpreted by microprocessor which calculates coordinates of where the screen was touched

96
Q

Resistive screen benefits (2)

A

Relatively inexpensive
Possible to use bare/gloved fingers or stylus to carry out an input operation

97
Q

Resistive screen benefits (3)

A

Screen visibility poor in strong sunlight
Does not permit multi-touch capability
Vulnerable to scratches + wears over time

98
Q

Logic gates

A

Electronic circuits which rely on on/off logic. NOT, AND, OR, NAND, NOR, XOR

99
Q

Logic circuit

A

Formed from a combination of logic gates and designed to carry out a particular task. Output will either be 0 or 1

100
Q

Truth table

A

Method of checking the output from a logic circuit, use all the possible binary input combinations depending on the number of inputs

101
Q

Boolean algebra

A

Form of algebra linked to logic circuits based on TRUE and FALSE

AS Computer Science (7 decks)

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