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Computer Science Revision > 1.2 Memory and Storage > Flashcards

1.2 Memory and Storage Flashcards

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1
Q

What is Primary Storage?

A

Holds data and instructions which CPU needs access to while a computer is running. The CPU can quickly acess data from primary storage than from secondary storage,
e.g. RAM, ROM, Registers, Cache

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2
Q

Does Primary Storage have a high storage capacity?

A

No. It has a relatively small storage capacity compared to secondary devices

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3
Q

What is secondary storage?

A

Secondary storage – non-volatile storage used to save data.
E.g. hard disk - measured in terabytes (TB)

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4
Q

What is ROM?

A

Small piece of read-only memory located on the motherboard. It contains the very first instructions of the computer.
Non-volatile
Uses – firmware, and BIOS information.

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5
Q

What is RAM?

A

Temporary storage of instructions and data for programs executed by the processor.
Uses – holds operating system and programs in use by CPU while computer is running. It is volatile (contents lost when power is turned off). Large compared to ROM.

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6
Q

Internal components of a computer

A

RAM, ROM, CPU, Hard Drive

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7
Q

What is the POST?

A

Power on Self Test - wakes up all the connected components and makes CPU aware of their existence

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8
Q

What is Virtual Memory?

A

Virtual memory allows computers to use hard disk space as an extension of RAM - when there is not enough physical RAM to store the open programs.

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9
Q

What happens when instructions are needed again?

A

A different program can be swapped out of RAM into virtual memory to make room for instructions now needed.

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10
Q

What happens when RAM is not executed?

A

Programs are transferred out to virtual memory and when RAM is needed, programs are transferred back to RAM from virtual memory.

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11
Q

Why is Secondary storage needed?

A

ROM is read-only and RAM is volatile. It is needed for storage of programs and data when power is turned off, semi-permanent storage of data that can change, backup of data files and archive of data files

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12
Q

What is the drive?

A

The device that reads and writes data from secondary storage

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13
Q

Media

A

What the data is actually stored on

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14
Q

What is optical storage?

A

`Consists of CD-R, CD-RW. DVD-RW, Blu-Ray
Low capacity compared to other types of storage, slow to access data

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15
Q

How do optical drives work?

A

By shining a laser at the media and processing the reflection from the media

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16
Q

What are pits and lands?

A

Where the surface of the disc is physically burned by the laser. Suitable for storing zeros and ones.

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17
Q

What is magnetic storage?

A

Consists of a hard disk drive, and tape. High storage capacity. Quick to access data. Has moving parts, which eventually fail. Hard disks perform better if defragmented

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17
Q

Disadvantages:

A

Slow access times, prone to scratches

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17
Q

Advantages:

A

Cheap, thin, light weight, portable

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17
Q

Advantages of magnetic storage:

A

Cheap, large capacity

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17
Q

Disadvantages of magnetic storage:

A

slow access times, fragile

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17
Q

What is solid state storage?

A

Consists of SSD, Memory sticks, Flash memory cards. Medium storage capacity. Very quick to access data. No moving parts, very reliable, no noise, low power, no need to defragment. Expensive compared to other types of storage

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18
Q

Advantages:

A

Durable, Fast access times

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19
Q

Disadvantages:

A

Cost, Limited read and writes

20
Q
A
21
Q

What is a bit (b) or binary digit?

A

Everything must be stored with only ones and zeros

22
Q

What is a nibble?

A

4 bits or half a byte

23
Q

What is a byte?

A

1 byte (B) = 8 bits

24
Q

What is a kilobyte?

A

1 Kilobyte (KB) = 1024 bytes - 2^10 : 1000 ~~ bytes - 10^3

25
Q

What is a megabyte? (1000KB)

A

1 MB = 1024^2 bytes - 10^6 - 1,000,000 bytes

26
Q

What is a gigabyte? (1000MB)

A

1 GB = 1024^3 bytes = 10^9 = billion bytes

27
Q

What is a terabyte? (1000GB)

A

1 TB = 1024^4 bytes = 10^12 = trillion bytes

28
Q

Petabyte (1000TB) :

A

1 PB = 1024^15 bytes = 10^15 = quadrillion bytes

29
Q

Why is data converted into binary to be processed through the computer?

A

With just two states, electronic components are easier to manufacture, therefore cheaper and more reliable. Examples of using two states to store data include RAM - capacitors with a charge or no charge - Optical disk - light reflected or not - Hard disk with magnetic disk representing north and south polarity and Memory stick - flash memory

29
Q

What is a binary digit?

A

A 0 or a 1.

30
Q

What is so special about bits?

A

With combining a series of bits, it’s possible to represent any kind of data, text, images, sound and commands.

31
Q

How do you calculate a text file?

A

Bits per character x Number of characters

32
Q

How to calculate a sound file?

A

Sample rate X Duration (s) x Bit depth

33
Q

How to calculate an image file?

A

Colour depth x Image height (px) x Image width (px)

34
Q

How to convert from denary to binary?

A

Divide by two method or binary number line method

35
Q

How to convert from binary to denary?

A

Add together the columns that have 1s in. e.g. 01100110 = 64+32+4+2 = 102

36
Q

What is the rule in adding binary?

A

0 + 0 = 1
0 + 1 = 0
1+ 1 = 0 carry 1
1+1+1 = 1 carry 1

37
Q

What is an overflow?

A

When the total from adding binary numbers can not be stored within the registers of a CPU. The largest number we can store in 8 bits is 255.

38
Q

How do we fix an overflow error?

A

Add an extra column on the left beyond the 128 with a weighting of 256 to store this number

39
Q

What is the denary number range?

A

0 - 255

40
Q

What is the binary number range?

A

00000000 - 11111111

41
Q

What is the hexadecimal range?

A

00 - FF

42
Q

Why ix hexadecimal used?

A

They are useful for representing large binary numbers in a smaller number of digits. They are used in computer science to represent colours, memory address, MAC addresses and much, much more

43
Q

What is Most Significant Bit?

A

The left-most bit in any representation - 128 is biggest value

44
Q

What is the Least Significant Bit?

A

The right-hand side is the least significant bit - 1 is lowest value

45
Q

What is binary left shift?

A

Multiplying (by 2)

46
Q

What is binary right shift?

A

Dividing (by 2)

47
Q

What is a character set?

A

A defined list of characters recognized by the computer hardware and software. With each character being represented by a single number.

48
Q

What is each character represented by?

A

A binary number

49
Q

Well known character sets:

A

ASCII - a 7 bit character set with 2^7 characters = 128

50
Q

What is Extended ASCII?

A

an 8 bit character set with 2^8 characters = 256

51
Q

What is Unicode?

A

24-bit character set with 2^24 characters > 16 million

52
Q
A

Computer Science Revision (5 decks)

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