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Computer Science > Memory and Storage 1.2 > Flashcards

Memory and Storage 1.2 Flashcards

1
Q

what are the uses of primary storage

A

RAM, ROM, registers and cache

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2
Q

why is primary storage needed

A

-access times are faster than secondary storage
-the time taken to complete operations such as the FED cycle is reduced

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3
Q

what are uses of secondary storage

A

operating system, programs and data are held here when not used

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4
Q

why is secondary storage needed

A

-for long term storage of programs and data that are currently not in use

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5
Q

what are uses of tertiary storage

A

storage used for backing up and archiving large amounts of data

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6
Q

what are features of primary storages

A

-they are volatile except ROM
-relatively small capacity compared to secondary hard drive
-loses memory when computer is turned off
-measured in GB
-very fast access compared to secondary storage

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7
Q

What is RAM

A

-temporary storage of instructions and data
-holds information being executed by the processor
-volatile
-holds operating system when the computer is running

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8
Q

what are features of secondary storages

A

-all non-volatile, when we turn power off, they still hold data stored on them
-much large storage capacity compared to primary storage
-measured in TB
-very slow access times compared to primary storage

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9
Q

what is ROM

A

-small piece of read only memory located on the motherboard (soldered)
-non-volatile
-contains very first instructions for the computer to properly boot up(bootstrap)
-software on ROM is called firmware
-is possible to update the BIOS on a ROM chip

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10
Q

function of the BIOS

A

-when the computer is powered on, the CPU reads instructions from ROM to perform self-checks and set up the computer
-(testing if memory is working, see what hardware is present and copy OS into RAM)
-Loads the operating system into RAM
-checks for hardware connected to the computer
-provides basic UI where some settings can be accessed (changing which storage device to lead the OS from)

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11
Q

what is virtual memory

A

-computers have limited amount of RAM
-when RAM is full/not enough physical RAM to store the open programs,
-programs that have not been used recently or not being currently executed to a location on the secondary storage known as virtual memory
-this frees up space in RAM
-programs are transferred back to RAM from virtual memory when they are needed
-allows the computer to remain operational

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12
Q

what is a drive

A

the device that reads and write data from secondary storage

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13
Q

what is media

A

what the data is actually stored on

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14
Q

advantages of magnetic storage

A

-Capacity - High storage
-Cost - low per gigabyte
-Speed - moderate red/write access

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15
Q

disadvantages of magnetic storage

A

-Durability - Moving parts can get damaged if dropped
-Portability - Heavy and bulky making them less convenient for transport
-Reliability - Prone to mechanical failure
-Noise - loud

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16
Q

advantages of optical storage

A

Cost - very low per gigabyte
Durability - No moving parts
Portability - small and no moving parts
Noise - silent

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17
Q

disadvantages of Optical Storage

A

Capacity - very low
Speed - very slow read/write speed
Reliability - Prone to scratches

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18
Q

advantages of solid state storage

A

-capacity - medium storage
-speed - very fast read/write access
-durability - no moving parts
-portability - small and no moving parts
-noise - silent

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19
Q

disadvantages of solid state storage

A

cost - very high per gigabyte
reliability - limited read/write cycles

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20
Q

what are factors for which storage device someone would use

A

-capacity
-speed
portability
-durability
-reliability
-cost

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21
Q

why do computers process data in binary

A

-computers consist of switches
-1 is represented as the switch being open, 0 represents switch being closed

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22
Q

why must happen to data before computers can understand and process it

A

-must be converted to binary

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23
Q

advantages of converting data to binary

A

allows computers to process it at high speeds, perform calculations and store data efficiently

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24
Q

what are character sets

A

-a character set is a defined list of characters recognised by the computers from their binary representation
-each character is represented by a unique binary number

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25
what are examples of well known character sets
-ASCII- a 7 bit character set with 2⁷ characters which = 128 (American standard code for information interchange) -Extended ASCII - an 8 bit character set with 2⁸ characters -UNICODE - a 24 bit character set with 2²⁴ character( more than 16 million)
26
how can images be represented
images can be stored in binary as bitmaps or vectors
27
what are bitmap pictures
they are constructed from coloured squares called pixels
28
what are vector pictures
they store the mathematics to draw coloured shapes
29
how are pixel stored
in binary, with RGB values (red green blue)
30
how do the number of bits per pixel vary
depends on the number of colours required. Number of colours calculated as 2 to the n, where n in the number of bits for each pixel
31
Colour depth
The number of bits stored per pixel in a bitmap image
32
what is metadata
-it is the information stored in an image file which helps the computer recreate the image on screen from the binary data in each pixel -additional data stored with the image to define the width, height, colour depth and colour palette -without metadata devices would not be able to display the image on screen as intended
33
how does the file size of the image change?
the greater the colour depth and resolution, the larger the file size
34
what is resolution
the number of pixels
35
what is sound file size and how do you calculate it
-it is the total number of bits in a sound. -(number of samples per second) x (number of bits per sample) x (length of samples in seconds)
36
what is bit depth
-the number of bits stored per sample -the higher the number of bits, the greater the quality of sound, and the larger the file size
37
what is sample rate
-the number of samples stored per second -the higher the number of samples per second, the higher the quality of the sound, and the large the file size
38
what is compression
-reducing the number of bits in a file -making the storage capacity of the file lower -making data transfer of the file quicker -useful because more data can be stored on a storage device, and transferred in a smaller amount of time
39
how is sound sampled
-sound is recorded by a microphone as an analogue signal (pieces of continually changing data) -analogue signals are converted into digital data (so computers can read and store sound files) using analogue to digital converters -to play the sound, digital data is converted into analogue using digital to analogue converter, and is amplified over speakers or headphones
40
effect of increasing bit depth
-sound sampled will be closer to the quality of the original recording -quieter sounded will also be picked up even if they happen at the same time as louder ones -larger file size
41
effect of increasing the sample rate
-analogue recording is sampled more often -better quality sound and more closely match the original recording -larger file size
42
what is lossy compression
-some of the data is lost and cannot be recovered -greatly reduces the file size -reduces the quality of the image/sound -suitable for images, sound and video -cannot be used on text and executable files
43
lossless compression
-none of the data is lost, it is encoded differently -can be turned back into original format -can be used on all types of data -is usually less effective than lossy compression -most suitable for documents and executable files
44
benefits of lossy compression
-less storage on a device as files are smaller -streaming and downloading files from the internet is quicker as less bandwidth is used -allows web pages to load more quickly in web browsers -commonly used- lots of software can read lossy files
45
cons of lossy
-loses data and file cannot be turned back into the original -cannot be used on text of software files and they need to retain all the information of the original -worse quality than original(normally unnoticeable)
46
benefits of lossless
-data is only removed temporarily so no reduction in quality -lossless files can be decompressed (turned back into the original) -can be used on text and software files
47
cons of lossless
only a slight reduction in file size, so a large bit of space on your device is used
48
examples of lossy files
-MP3 (audio) -AAC (audio) -JPEG (image)
49
examples of lossless files
-FLAC (audio) -Zip (files and folders) -PNG (image)
50
what is volatile memory
-it is temporary memory. It requires power to retain its data
51
what is non-volatile memory
-it is permanent memory - it keeps its contents even when it has no power
52
what happens to OS when the computer boots up
it is copied from the secondary storage to the RAM
53
what happens to applications, files and documents when they are opened
they are copied from the secondary storage to RAM. They stay in RAM until the files or applications are closed
54
advantages of using HDD to SDD
-cheaper -higher capacity -longer read/write life
55
advantages of using SDD to HDD
-faster data transfer speeds -no defragmenting -more shock-proof -silent
56
advantages of Optical
-very cheaper per GB -portable -not damaged by water or shocks
57
why has use for optical discs declined
-faster internet speeds, streaming and download services have removed the need for optical discs -very slow read and write speeds, poor reliability and low capacity
58
what is a left shift
-every number is shifted to the left -for every place shifted left, the number is doubled
59
what is a right shift
-every number is shifted to the right -for every place shifted right, the number is halved
60
what is a overflow
-when extra bits are needed after performing a left shift -computers usually deal with these extra bits by storing them elsewhere
61
what happens when you perform a right shift
-bits 'drop off' can happen at the end
62
what can left and right shifts cause if they over flow and drop off
-lead to a loss of accuracy/data -can cause software to crash if it does not have a way of dealing with the extra bit when an overflow happens
63
what happens when you press a key
-a binary signal is sent to the computer telling it which key you pressed. -the computer then uses the character set to translate the binary code into a particular character
64
how many bits is in ASCII and how many different characters are tehre
-7 bits -128 characters
65
how man bits per character in unicode and how many different characters are there
-16 bits -149,186 characters
66
how many bits in extended ASCII
-8 bits -256 characters
67
why is UNICODE helpful
-covers all major languages, unlike ASCII
68
formula for file size(text)
-number of bits per character x number of characters = file size in bits
69
formula for file size(image)
image resolution x colour depth = width x height x colour depth = file size in bits
70
disadvantages of virtual memory
-can make a computer sow to respond when switching between applications as data transfer speeds from secondary storage are much slower than from RAM
71
why is secondary storage needed
-secondary storage is needed to store data long term -it is non-volatile, which means it will retain data when power is off -computers could not function without permanent data storage, as all software and data would be lost when switched off -secondary storage has a high capacity so you can store more data
72
nibble
4 bits/half a byte
73
Formula to find the size of an image file
(Resolution of height x width) x (colour depth in bytes) = file size in bytes
74
Denary
-A number system that is made up of 10 digits(0-9) -referred to as base-10
75
Why is analogue converted into digital form
-analogue sound wave is sampled -amplitude is measured at regular intervals -each sample is stored as a binary number -the binary number for each sample stored sequentially

Computer Science (15 decks)

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