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Computer Science OCR GCSE > 1.2 Memory and storage > Flashcards

1.2 Memory and storage Flashcards

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1
Q

1.2.1 Primary storage (memory)

The need for primary storage

A
  • low capacity
  • internal storage
  • directly accesed from the CPU
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2
Q

1.2.1 Primary storage (memory)

RAM vs ROM

A

RAM:
* volatile (temporary) storage
* stores currently running instructions/data
* able to read and written into

ROM:
* non-volatile
* stores boot program to turn on a computer
* read only memory

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3
Q

1.2.1 Primary storage (memory)

Virtual memory

A
  • using hard disk drive as an extension of RAM for when there is insufficient space on RAM
  • unused data in RAM is moved to hard drive, so new & needed data can be put into the RAM
  • allows users to run more programs simultaneously with less system slow down
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4
Q

1.2.2 Secondary storage

The need for secondary storage

A
  • non-volatile
  • save/stores repeatedly accessed data
  • slower to access than primary data - further away from CPU
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5
Q

1.2.2 Secondary storage

Optical storage

A
  • eg: CDs, DVDs, Blu-Ray
  • read and write, using lasers
    Pros: thin, very portable, cheap
    Cons: low capacity, not durable, slowest access speed
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6
Q

1.2.2 Secondary storage

Magnetic storage

A
  • eg: hard disk drive, tape drivers
    pros: large capacity, quicker than optical, cheap
    cons: not durable, not portable, slow access speed
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7
Q

1.2.2 Secondary storage

Solid state

A
  • eg: solid state drives, USB memory sticks, SD cards
    Pros: high capacity, durable, portable, fastest access speeds
    Cons: expensive, per gigabyte
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8
Q

1.2.2 Secondary storage

which storage type is the best and worst?

A

Solid state is the best
Optical is the worst

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9
Q

1.2.3 Units

Storage unit order

A
  1. bit
  2. nibble
  3. byte
  4. kilobyte
  5. megabyte
  6. gigabyte
  7. terabyte
  8. petabyte

Kites Make Great Toy Planes

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10
Q

1.2.4 Data storage - Numbers

Hex, binary, denary conversion

A

Hex to denary:
* base 16, letter.
* 2A = (2x16)+10 = 42 in denary

Denary to hex:
* 27 = 27/16 = 1r11 = 1B

Binary to hex:
* split into nibble and add and calculate
* 11100101 = 1110 | 0101 = 14 | 5 = 14 +5 = E5

Hex to binary:
* 3B
* 3 = 0011
* B = 11 = 1011
* 3B = 00111011

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11
Q

1.2.4 Data storage - Numbers

Binary shifts

A

shift left = multiple
shift right = divide

eg: shift right by 3 place:
01010001 = 00001010
cut 3 digits off from the right, replace with 3 0s on the left

shift 1 = effect 2 | shift 2 = effect 4 |shift 3 = effect 8

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12
Q

1.2.4 Data storage - characters

definition of character set

A

Character set: a table that matches together a character and a binary value.
Necessary as they allow computers to exchange data and humans to input characters

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13
Q

1.2.4 Data storage - characters

ASCII vs Unicode

A

ASCII:
* doesn’t take much memory
* uses 1 byte to provide 256 characters
* enough for english language, can’t be used for different languages

Unicode:
* uses more memory space
* uses 2 bytes to provide 65,536 characters
* allows different languages and thousand of symbols & emojis

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14
Q

1.2.4 Data storage - images

How is an image presented to a computer?

A
  • as a series of pixels: each pixel has a specific colour, with a specific code
  • also represented in binary
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15
Q

1.2.4 Data storage - images

What is metadata

A
  • stores additional image information
  • eg: height, width
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16
Q

1.2.4 Data storage - images

What does the quality of the image affect?

and how?

A
  • resolution: higher resolution = less pixelated the image, when zoomed in, it is still clear to see the image
  • colour depth: the more colours there are, the more detailed and realistic the image can look
17
Q

1.2.4 Data storage - images

What does the image size affect?

and how?

A
  • Resolution: the higher the resolution, the higher the file size as there are smaller pixels in a set height/width so more data = higher file size
  • Colour depth: if there are more bits to store a colour of a pixel, then there is more data so higher image size
18
Q

1.2.4 Data storage - images

Formula for file size of images

A

Resolution x colour depth

19
Q

1.2.4 Data storage - Characters

Formula for file size of text files

A

bits per character x number of characters

20
Q

1.2.4 Data storage - Sound

How can sound be sampled?

A

The amplitude of the analogue sound wave is measured and recorded in binary at specific intervals

21
Q

1.2.4 Data storage - Sound

Sample rate

A
  • The number of times per second, the amplitude of the wave is measured
  • measured in Hertz
  • Higher sample rate = better audio quality because digitial version closely resembles the analogue wave
  • Higher sample rate = larger data size because more data is stored
22
Q

1.2.5 Compression

The need for compression

A
  • makes its file size smaller
  • takes less storage space (more files can be stored)
  • files can be transferred quicker (since they are smaller)
  • files can be read from/written to quicker
23
Q

1.2.5 Compression

Lossy compression

A
  • reduces file size
  • removes data permanently (irreversible)
  • quality decreases
24
Q

1.2.5 Compression

Lossless compression

A
  • file size reduce
  • data not permanently removed (reversible)
    *

Computer Science OCR GCSE (7 decks)

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