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A Level OCR Computer Science > Section 1 - Components Of A Computer > Flashcards

Section 1 - Components Of A Computer Flashcards

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1
Q

What does the control unit do?

A

Controls and coordinates the CPU, accepts and decodes instructions, manages their executions and the resulting data storage.

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2
Q

What is the system bus?

A

A set of 3 busses, the control, data and address busses.

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3
Q

What is meant by each bus being a shared transmission medium?

A

Only one device can transmit along a bus at any one time.

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4
Q

What is the control bus and what is it for?

A

The control bus is a bi-directional bus used to transmit command, timing and specific status info between components.

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5
Q

What are 6 examples of control lines within the control bus?

A

Bus request (to use the data bus)
Bus grant (to use the data bus)
Memory write (data on the data bus gets written to the addressed location)
Memory read (data from addressed location gets put on the data bus)
Interrupt request (device requesting CPU access)
Clock

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6
Q

What is the data bus and its purpose?

A

The data bus is usually 8, 16, 32 or 64 lines for bidirectional transmission of data and instructions

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7
Q

What is a ‘word’ in terms of memory

A

The word size is the amount of bits per piece of internally divided memory. A CPU can only handle word sizes specific to its architecture

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8
Q

What is the address bus and what does it do?

A

Transmits the memory address of words to be used as operands in program instructions

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9
Q

What is the ALU and what does it do?

A

The arithmetic logic unit performs basic arithmetic and Boolean logic operations.

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10
Q

What is the accumulator for?

A

Stores all of the results from the ALU

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11
Q

What does the PC do?

A

Stores the address of the next instruction to be executed, this could be the next sequential address or the next address provided by a branch or jump instruction, copied from the CIR

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12
Q

What does the CIR do?

A

Stored the current instruction being executed, divided into operand and opcode

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13
Q

What does the MAR (memory address register) do?

A

Stores the memory address location that data is to be fetched from or written to

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14
Q

What does the MDR (memory data register) do?

A

Temporarily stores the data that has just been read from memory or is going to be written to memory.

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15
Q

Simply describes what happens in the registers during the fetch phase of the fetch-decode-execute cycle.

A
  1. The address of the next instruction is copied from the PC to the MAR
  2. The instruction at that address is copied to the MDR and the PC is incremented
  3. The contents of the MDR are copied to the CIR
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16
Q

Simply describe what happens during the decode part of the fetch-decode-execute cycle

A

The instruction in the CIR is decoded into opcode and operand and the opcode is interpreted to find out the type of instruction given and the hardware needed to execute it.

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17
Q

What 3 things, useful in the FDE cycle does the operand hold?

A

The address of the data held to be executed (copied to MAR), or,
The actual data to be operated on (copied to MDR)
The data to be operated on but needs to be passed to the ALU

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18
Q

What 3 main factors affect CPU performance the most?

A

Clock speed
The number of cores, or duplicate processors all on one chip
The amount and type of cache memory

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19
Q

How does the CPU respond to the system clock?

A

Each ‘pulse’ of the system clock (change from 0 to 1) starts a processor activity

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20
Q

How is clock speed measured and what is a typical clock speed

A

1 Hertz or 1Hz is 1 operation per second. Typical clock speeds range from 2 - 4GHz

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21
Q

Why might a quad core processor not run 4 times faster than a single processor?

A

Software is sometimes not designed to take advantage of more than one core

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22
Q

What is a cache for and what happens when they fill up?

A

They store recently fetched instructions so they can be grabbed much faster if needed again. Old instructions are overwritten if unused.

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23
Q

What is pipelining?

A

When a processor does more than one thing simultaneously to increase utilisation. For example fetching an instruction while decoding another and executing another.

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24
Q

How does word size affect memory size?

A

The word size is the max number of addresses that can be referenced, making the word size the maximum amount of memory possible for a computer

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25
Q

How does a data bus limit the size of values to be used within a computer?

A

The size of the data bus is the maximum number of bits that can be used to store a single value. I.e. a 16 but wide data bus can only store a maximum number of 2^16 in one address

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26
Q

What is contained in the opcode of an assembly instruction?

A

The basic machine operation and then the addressing mode.

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27
Q

What is the von Neumann architecture?

A

The von Neumann architecture specifies that a single bus is used for both data and instruction transmission.

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28
Q

What is the Harvard architecture?

A

A computer that has physically separate memories for instructions and data

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29
Q

Compare the von Neumann architecture against the Harvard architecture

A

Its used in conventional processors and servers
Data and programs share the same memory
One bus is used to transfer data and instructions
Programs can be optimised in size

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30
Q

Compare the Harvard architecture against the Von Neumann architecture

A

Used in digital signal processing and embedded systems, mobile communication systems and more
Instructions and data are held in separate memories
Parallel data and instruction buses may be used
Programs tend to be large

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31
Q

How do some high performance CPU’s utilise a mix of the Von Neumann and Harvard architectures?

A

They use a shared memory for the CPU but the cache is separated into an instruction cache and a data cache.

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32
Q

What is meant by a CISC?

A

A CISC is a complex instruction set computer which is a computer that utilises a reduced amount of assembly language instructions by using many simplified and specific instructions.

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33
Q

Why is a CISC bad?

A

CISCs have too many instructions that never get used but are all built into the hardware components

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34
Q

Why is a CISC good?

A

The compiler has much less work to do in converting from high-level code and because the code is short, takes up much less RAM.

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35
Q

What is a RISC?

A

A Reduced Instruction Set Computer has the simplest possible assembly language instructions. This causes larger programs but fewer built-in instructions.

36
Q

What are some advantages of RISCs?

A

Since every instruction only takes one clock cycle, pipelining is possible, making RISCs often faster than CISCs.

37
Q

What are some disadvantages of RISCs?

A

Since more instructions are needed to carry out the same operation as CISCs, more RAM is required to store the machine code instructions and the compiler has to do more work.

38
Q

What is meant by a co-processor and what are they for?

A

A co-processor is an extra processor used to supplement the primary processor by performing specific operations such as graphic processing, floating-point arithmetic, digital signal processing and more.

39
Q

How do multi-core and parallel systems achieve higher performance than normal computers?

A

By using more than one CPU core or more than one processor in parallel alongside a job scheduler, every processor works in parallel on a separate job, making this very fast.

40
Q

How does a GPU work?

A

A GPU contains thousands of small, efficient cores designed for handling many tasks simultaneously

41
Q

Give 4 examples of what GPUs are used for.

A

Most commonly, graphics processing, but also machine learning, image processing and financial transactions

42
Q

What are barcodes (3) and QR codes (2) used for nowadays?

A

Barcodes: identifying medical samples, products and parcels.
QR codes: website links, ticket information, etc

43
Q

What are the 4 types of barcode readers?

A

pen-type readers,
laser scanners,
CCD readers,
camera-based readers

44
Q

How does a pen-type barcode scanner work?

A

A pen-type scanner is dragged across a barcode and shines light on the page while measuring the intensity of the reflected light with a photodiode. It then recreates the barcode digitally.

45
Q

What are some advantages and disadvantages of pen-type barcode scanners?

A

They are simple, durable and portable but they must come into direct contact with a barcode to be able to scan it.

46
Q

What are some applications of pen-type barcode scanners?

A

Their portability and durability make them suitable for laptops and very low-volume scanning applications.

47
Q

How does a laser barcode scanner work?

A

Just like a pen-type scanner, just with a laser instead of a light.

48
Q

What are some good applications of laser barcode scanners?

A

In-counter supermarket scanners and low-volume economical applications.

49
Q

how do camera-based barcode scanners work?

A

They use an imaging scanner and image processing techniques to decode a barcode on almost any surface, even if poorly printed.

50
Q

What are some non-consumer applications of camera-based barcode scanners?

A

Age verification scanners with driving licenses,
Coupon scanning,
Event Ticketing

51
Q

How may consumers utilise camera-based barcode scanners?

A

To scan a website link,
To play an MP3 when scanned,
To display nutrition information on a product

52
Q

How does a digital camera work?

A

A digital camera uses a CCD or CMOS sensor which captures light. The binary information from these sensors is then copied to the camera’s memory card to be recreated later.

53
Q

How do CMOS and CCD sensors compare in digital cameras?

A

A CCD scanner is a high-quality, reliable sensor when compared to a CMOS sensor but can use up to 100 times more power than a CMOS sensor.

54
Q

How does an RFID chip work?

A

An RFID (radio frequency identification) chip is a small chip that can receive and transmit data via radio frequencies.

55
Q

How does a passive RFID chip work?

A

A passive RFID chip has a long, coiled-up antenna which can receive a signal and become energised by electromagnetic power to transmit a response to a reader.

56
Q

How does an active RFID chip work?

A

An active RFID chip contains a battery and actively transmits a signal to be received.

57
Q

Where are passive RFID chips used? (4)

A

Passive chips are used in some groceries, CDs, travel cards and bank cards

58
Q

Where are active RFID chips used? (3)

A

Anything that will be read from farther away than passive chips such as cars or marathon runners.

59
Q

What does an output device do?

A

It takes input from a computer and converts it into a form that a human can interact with.

60
Q

Why are LED screens better than older technology?

A

They reach maximum brightness almost immediately.
They have sharp colours.
They are very small and thin.
They use very little power and heat

61
Q

What advantages do OLED screens have over LED screens?

A

They are flexible as they are made of plastic, not glass,
They are even thinner than an LCD,
They are brighter and consume less power,
OLEDs can respond much much faster than LCDs (higher refresh rate)

62
Q

How does a laser printer work?

A

Laser printers use a laser to heat toner which gets printed onto a piece of paper. This can be done for different colours.

63
Q

What are some advantages and drawbacks of laser printers?

A

They are fast and high-quality but do not have enough quality to print photorealistic images

64
Q

How does an inkjet printer work?

A

An inkjet printer sprays minute dots of ink onto a page to create very high-quality images

65
Q

Why are inkjet printers good?

A

They are cheap and make very high-quality images.

66
Q

Why might someone choose a laser printer over an inkjet printer?

A

Laser printers are much faster and can print a lot in one go whereas inkjet printers are slow.

67
Q

How does a dot-matrix printer work?

A

A dm printer or impact printer has a matrix of pins that strike a page through an inked ribbon to make letters

68
Q

Why are matrix printers bad?

A

They are slow, noisy and do not print at high-quality

69
Q

Why are matrix printers good?

A

They can operate in damp or dirty environments

70
Q

What are some common applications of 3D printers?

A

They can be used to make car parts, aeroplane parts, medical equipment, fashion accessories and even firearms.

71
Q

What benefits do projectors have within a classroom setting?

A

Having an image to focus on in class can aid concentration
Watching educational videos can add interest to lessons
Lessons can be saved and recreated instead of retaught every time.

72
Q

What uses do computer speakers have?

A

aside from music and video, speakers can be used for verbal instructions, reading text and giving alerts

73
Q

What are actuators?

A

Actuators are small motors used to control systems

74
Q

Where are actuators used?

A

To open windows,
Star or stop pumps,
turn a wheel,
move an aircraft aileron,
control smart home devices

75
Q

What is the main need for secondary storage in a computer?

A

Secondary storage is high capacity and is non-volatile

76
Q

How does a hard disk work?

A

A hard drive uses rotating disks coated with magnetic iron particles which become polarised to either a north or south state representing 1s and 0s. The disk is spun quickly and is either read or written to by a drive head.

77
Q

How is the space on a hard drive organised?

A

Tracks divide the disks horizontally and sectors (like a sector of a circle) divide the disks vertically.

78
Q

How is data stored on a disk?

A

A laser burns pits into a disk and leaves unburnt lands to both represent 1s and 0s.

79
Q

How are CD-ROM disks and Blu-Ray disks different?

A

A blue ray disk can hold up to 50GB and a CD-ROM can hold around 700MB due to the shorter wavelength of blue light used in Blu-ray disks

80
Q

How does a DVD-RW (rewriteable) disk work?

A

a phase change alloy that can swap between reflective and nonreflective coats the disk, making it rewritable

81
Q

How does an SSD work?

A

An SSD delivers current along the bit and word lines to activate electrons, forcing some into a floating gate, trapping them when the current is removed. The state of the NAND flash memory cells is then determined by measuring the charge in the floating gate. To overwrite data, a block is first erased and then replaced.

82
Q

Why are SSDs good?

A

They are incredibly fast, do not need to be defragmented, and are very portable, power efficient, and silent.

83
Q

What does it mean to say that flash memory is robust?

A

It is resistant to shocks and vibrations

84
Q

What are the two types of pipelining in modern processors?

A

Instruction and arithmetic pipelining (essentially two different pipelines, one for instructions and the other arithmetic)

85
Q

What does BD-R mean?

A

A Blu-ray disk which can be written once at home.

86
Q

What does the accumulator do in the FDE cycle?

A

Stores all input/output
Holds results from the ALU
Checks for conditional branching
Stores data from the MDR/MAR

87
Q

How are RISC compilers different from CISC compilers?

A

RISC compilers are more complex than CISC and will take longer to compile

A Level OCR Computer Science (13 decks)

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