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Computer science > 1.2 Memory And Storage > Flashcards

1.2 Memory And Storage Flashcards

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1
Q

What does primary storage consist of

A

RAM (random access memory)
ROM (read only memory)

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2
Q

What is ROM

A

Small piece of read only memory
Non volatile (contents remain when power turned off)
Programs may be stored in it in embedded systems
Contains very first instructions for computer when its turned on (bootstrap)

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3
Q

What’s RAM

A

Temporary storage of instructions & data
Volatile (contents lost when power is turned off)
Read and write
Much faster than the hard disk
Holds operating system, programs and data in use by CPU when computer’s running

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4
Q

How does virtual memory work

A

Needed when not enough physical RAM to store open programs
Held on hard disk
Programs swapped to virtual memory from RAM when not currently in use
Programs swapped back to RAM from virtual memory when they’re needed

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5
Q

Why is secondary storage needed

A

ROM is read only + for bootstrap and RAM is volatile + for the working memory

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6
Q

What’s secondary storage needed for

A

Storage of programs when power is turned off
Long term storage
Backup of data files

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7
Q

What’s optical storage + examples

A

CD, DVD, blu-ray
Low capacity compared to other types of storage
Slow to access data
Lightweight + portable

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8
Q

What’s magnetic storage + examples

A

Hard disk drive, magnetic tape
High storage capacity
Quick to access data
Has moving parts - eventually fail

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9
Q

What’s solid state storage + examples

A

SSD, memory sticks, flash memory cards, SD cards
Medium storage capacity
Very quick to access data
No moving parts - very reliable/durable
Limited number of read/write cycles
Expensive per gig compared to other types of storage

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10
Q

Why do we use binary

A

A CPU is made of millions of transistors that can be in one of two states - on or off

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11
Q

How do you calculate text files sizes

A

Bits per character x number of characters

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12
Q

How do you calculate image file size

A

Colour depth x image height x image width

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13
Q

How do you calculate sound file size

A

Sample rate x duration in seconds x bit depth

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14
Q

What are the placeholder headings in binary

A

128 64 32 16 8 4 2 1

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15
Q

Why do we use hexadecimal

A

Binary can be difficult to work with, its shorter, it can easily be converted to/from binary as theres 1 hex digit per nibble and hex is less susceptible to errors

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16
Q

What letters represent 10 - 15 in hex

A

10 = A
11 = B
12 = C
13 = D
14 = E
15 = F

17
Q

What are the hex placeholder

A

16 1

18
Q

What do you do when you shift left in binary

A

Multiply

19
Q

What do you do when you shift right in binary

A

Divide

20
Q

What is a character set

A

A defined list of characters recorded by the computer

21
Q

What is the term character set used for

A

To describe the possible characters that can be represented in a computer system

22
Q

What is ASCII

A

A 7 bit character set with 128 characters (2^7)

23
Q

What is extended ASCII

A

An 8 bit character set with 256 characters (2^8)

24
Q

What is Unicode

A

A 16 bit character set with 65,536 characters (2^16)

25
Q

How does an overflow error happen

A

When the result of a binary addition is greater than 8 bits

26
Q

What’s a pixel

A

The smallest part of an image

27
Q

What’s metadata

A

Data about data eg = height, width, colour depth, type of image, when created, date/time, location etc.

28
Q

How must analogue sound be recorded

A

Digitally in binary

29
Q

What affects sound quality

A

How the often the height is recorded (sample rate) and the accuracy which it recorded (bit depth)

30
Q

What affects a sounds file size

A

Duration of the recording

31
Q

Calculate the total number of bits in a sound file size

A

Number of samples per second x number of bits per sample x length of sample in seconds

32
Q

What is bit depth

A

The number of bits stored per sample

33
Q

What is sample rate

A

Number of samples stored per second

34
Q

How is analogue converted to digital

A

An analogue sound wave is sampled, the height of the wave is measured at regular time intervals. Each samples stored as a binary number

35
Q

What’s compression

A

Reducing the number of bits in a file

36
Q

What does compression do

A

Makes file size smaller
Makes data transfer to the file quicker
Faster upload/download speed

37
Q

Lossy compression characteristics

A
  • Some data is lost permanently - cant be recovered
  • greatly reduces file size
  • reduces image, video or sound quality but not enough for a human to notice
  • cant be used on text and program code as parts will be missing
38
Q

Lossless compression characteristics

A
  • no data is lost - encoded differently
  • can be turned back to original format
  • usually less effective than lossy t reducing file size
  • most suitable for text documents and program code as

Computer science (3 decks)

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