2.6 Data Representation COMPLETE Flashcards by Nathan Kwok

What is the order of data size?

Bit - single digit (0 or 1)
Nibble - 4 bits
Byte - 8 bits
Kilobyte - 1024 bytes
Megabyte - 1024 KB
Gigabyte - 1024 MB
Terabyte - 1024 GB
Petabyte - 1024 TB

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How do computers understand binary?

They don’t understand the numbers 1 and 0, they understand flashes of electricity that pass through the transistors.
1 = Electricity pulse
0 = No electricity pulse

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What number system is binary?

Base 2:

2 possibilities - 1 or 0).

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Define vector

An image drawn by a set of mathematical formulas and can be scaled infinitely without any loss in quality.

Every line and shape has a value that changes when the image expands.

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Define bitmap

Page is divided into an invisible grid and each pixel is assigned a colour in binary (colour depth).

Higher bit depth = Higher image quality.

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What is PPI and DPI?

Pixels per inch.

Dots per inch.

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What happens if a pixel is to represent more than 1 colour?

We need to use more bits to make a range of colours available.

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How do you find out how many bits represent colours?

2 to the power of the number of bits = number of colours.

1 bit = 2 colours.
2 bits = 4 colours.
3 bits = 8 colours.

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What happens with greater colour depth?

The more:
Realistic colours there are
Data needs to be stored.
File size on the disk is needed.

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What happens with higher resolution?

There are more pixels, higher quality and higher image file size.

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What is digital sound broken down into?

Thousands of samples per second - each of which are stored as binary data.

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What does the quality of the samples depend on?

1) Sample frequency.
2) Sample size / bit depth.
3) Bit rate.

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Define sample rate

No. of audio samples captured every second.

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Define analogue

Made up of a variation of dynamic and frequencies.

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Define sampling

Recording snippets of sounds at set intervals.

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Define character set

The possible characters that can be represented in a computer system.

E.g. ASCII and Unicode.

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Define metadata

Image data that allows the computer to recreate the image from the binary data in the file.

Examples:
Dimensions.
Number of bits per pixel.
Location.
Data and File type.

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Define image size

Width and height of a bitmapped image, measured in pixels.

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If an image has its colour depth increased what is the effect?

The file size is bigger.

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Define overflow error

When the binary number is too big than actually possible

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What are the hexadecimal numbers compared to denary numbers?

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

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Define lossy compression

The file is compressed and data is lost. It compresses more than lossless

Should be used in audio files.

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Define loseless compression

The file is compressed; no data has been lost (file size is just smaller, but it isn’t as compressed as lossy ).

Should be used in text documents.

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What is the effect of multiplying the binary number by 2?

The number is shifted to the left by 1 bit

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What is the effect of dividing a binary number by 2?

The number is shifted to the right by 1 bit

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Define underflow

When the binary number is too small than actually possible

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All data processed by a computer must be converted into ______ format

binary

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A computer processor uses billions of ___________ acting as switches, which only act on the binary states on and off

transistors

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All data and instructions in a computer are represented by…

the binary digits 1 (on) and 2 (off)

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What binary digit represents ‘on’?

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What binary digit represents ‘off’?

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To be processed, instructions and data are converted to…

strings of 1s and 0s

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Images and sounds must be _________ to be processed

digitised

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What do inputs such as the keyboard and mouse send to the processor to be processed?

Combinations of 1s and 0s

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One unit, either a 1 or a 0, is called a…

bit

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What is bit short for?

Binary digit

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True/False: More than one digit is needed to represent an item of data (such as a letter), in binary

True

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True/False: Bits are organised into groups

True

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4 bits = 1…

nibble

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8 bits = 1…

byte

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True/False: Bytes are grouped into small units

False, they are grouped into larger units

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How many bytes are in a kilobyte?

1000

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How many kilobytes are in a megabyte?

1000

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How many megabytes are in a gigabyte?

1000

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How many gigabytes are in a terabyte?

1000

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How many terabytes are in a petabyte?

1000

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What is the abbreviation for kilobyte?

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What is the abbreviation for megabyte?

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What is the abbreviation for gigabyte?

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What is the abbreviation for terabyte?

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What is the abbreviation for petabyte?

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How many bytes are there exactly in a kilobyte?

1024

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When performing calculations, how many bytes do we say are in a kilobyte?

1000

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The binary system is a base-_ number system

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Why is the binary system a base-2 number system?

It uses two digits, 0 and 1

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The denary system is a base-__ number system

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Why is the denary system a base-10 number system?

It uses 10 digits, 0 to 9

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The hexadecimal system is a base-__ number system

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Why is the hexadecimal number system a base-16 number system?

It uses 16 digits, 0 to 15

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In any system, the value associated with any digit is given by its…

place value

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The value of each position in place value increases as the…

power of its base

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What is the value of the 1st digit in an 8-bit binary number?

128

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What is the value of the 2nd digit in an 8-bit binary number?

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What is the value of the 3rd digit in an 8-bit binary number?

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What is the value of the 4th digit in an 8-bit binary number?

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What is the value of the 5th digit in an 8-bit binary number?

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What is the value of the 6th digit in an 8-bit binary number?

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What is the value of the 7th digit in an 8-bit binary number?

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What is the value of the 8th digit in an 8-bit binary number?

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What is 10 to the power of 7?

10,000,000

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What is 10 to the power of 4?

10,000

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True/False: You can convert denary numbers with values from 0 to 255 into 8 bit binary numbers

True

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To convert numbers above 255 to binary, more ____ are required than 8 bit binary

bits

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What are denary numbers also called?

Decimal numbers

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Convert 234 to binary

11101010

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Convert 42 to binary

00101010

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Convert 87 to binary

01010111

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Convert 67 to binary

01000011

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Convert 12 to binary

00001100

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Convert 6 to binary

00000110

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Convert 124 to binary

01111100

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Convert 183 to binary

10110111

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Convert 132 to binary

10000100

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Convert 245 to binary

11110101

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How can you check you are correct in a denary to binary conversion?

By converting your binary number back into a denary number

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True/False: Binary numbers can also be converted to denary numbers

True

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What is 10001010 in denary?

138

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What is 01011101 in denary?

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What is 11010110 in denary?

214

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What is 00011010 in denary?

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What is 10100101 in denary?

165

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What is 10101010 in denary?

170

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What is 01010101 in denary?

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What is 10010101 in denary?

149

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What is 1 + 0 in binary addition?

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What is 0 + 0 in binary addition?

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What is 1 + 1 in binary addition?

10, you need to write the 0 and carry the 1 to the left

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When do overflow errors occur?

When a calculation produces a result that is greater than the computer can deal with

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What is the issue with the result of the binary addition 10110101 + 11001111?

There will be an overflow error (110000100)

What is wrong with the number 110000100?

It cannot be represented by an 8 bit number - a 9th bit is required. This is an overflow

Why must programmers make allowances for errors such as overflow?

To prevent serious errors or disasters

Binary shifts are used when…

multiplying or dividing binary numbers by powers of 2

Binary shifts are the equivalent of… (in terms of denary)

multiplying denary numbers by a power of 10 and moving the digits to the left, and writing zeros at the right-hand end

When you divide binary numbers by powers of 2, you move bits to the…

right

What is a right shift?

Moving bits of a binary number to the right

True/False: Right shifts make binary numbers larger

False, they make them smaller

True/False: Left shifts divide binary numbers

False, they multiply them

Hexadecimal is a base-__ number system

Hexadecimal numbers need __ digits

There are no denary digits beyond _

How are denary numbers from 10 to 15 represented in hexadecimal?

With the upper case letters A to F

How is the denary number 10 represented in hexadecimal?

How is the denary number 11 represented in hexadecimal?

How is the denary number 12 represented in hexadecimal?

How is the denary number 13 represented in hexadecimal?

How is the denary number 14 represented in hexadecimal?

How is the denary number 15 represented in hexadecimal?

What symbol is used to signify that a number is given in hexadecimal notation?

True/False: All denary numbers up to 255 can be represented by hexadecimal numbers with only two digits

True

All denary numbers up to 255 can be represented by hexadecimal numbers with only _ digits

Hexadecimal numbers are used to help programmers…

manipulate large binary numbers

True/False: Computers use hexadecimal numbers

False, they only understand binary

Hexadecimal numbers represent long binary numbers using…

fewer digits

How do hexadecimal numbers represent long binary numbers using fewer digits?

Every 8 digits of a binary number can be represented by two hexadecimal digits

When converting binary to hexadecimal, first you must split the 8 byte into…

two 4-bit nibbles

When converting binary to hexadecimal, once you have split the 8 bit byte into two 4-bit nibbles you…

convert the bits in each nibble into denary numbers using the place value

When converting binary to hexadecimal, after you have converted each nibble into denary numbers using place value you…

add these together to give the hexadecimal

True/False: Converting hexadecimal to binary reverses the process of converting binary to a hexadecimal number

True

When converting hexadecimal to binary, each hecadecimal digit is first converted to…

denary

After each hexadecimal has been converted to denary, when converting hexadecimal to binary, what is each denary number converted to?

A nibble

After denary numbers are converted to nibbles, when converting hexadecimal to binary, what happens to the nibbles?

They are combined to give the binary number

Why is hexadecimal notation used?

To help humans cope with long strings of binary digits - they are much shorter in hexadecimal

True/False: MAC addresses are given in hexadecimal form

True

When a computer malfunctions, error code numbers are usually given in ___________ form

hexadecimal

True/False: Hexadecimal is used to represent numerical values in assembly language

True

True colour uses __ bits to code every available colour variation

Each colour variation is represented by three 8 bit numbers that can be simplified to…

3 2-digit hexadecimal ones

It is far easier/harder to remember and enter the six digits of a hexadecimal number than the 24 digits of a binary number

easier

Check digits are used to…

ensure that a sequence of numbers has been entered correctly

Transcription errors

Errors made when entering data

Check digits are used to flag up what type of errors?

Transcription errors

Give an example of a code that uses check digits

Any from product codes/barcodes and ISBNs on books

The value of the check digit is usually calculated from…

the other data being sent

Computers represent text characters, numbers and symbols in binary as…

strings of 1s and 0s

What does ASCII stand for?

American Standard Code for Information Interchange

Text and characters are represented by…

ASCII code

ASCII is a _-bit code

There are ___ code sequences representing english characters and control actions such as space and shift

128

Give an example of a control action

Any from space, shift, etc

The _________ ___ is the list of binary codes that can be recognised by the computer hardware and software

character set

ASCII codes are grouped according to…

function

What is included in the ASCII code group 0-32?

Control codes such as shift and space

What is included in the ASCII code group 65-90?

Upper case characters such as A, Z

Extended ASCII code uses _ bits

The fact that extended ASCII uses 8 bits means there are ___ code sequences

256

What does extended ASCII include that ASCII doesn’t?

Mathematical characters such as pie and symbols for graphics

Extended ASCII code has/has not been standardised in the same way as the 7-bit code has

has not

In terms of extended ASCII code, different manufacturers use different codes for different __________

characters

Extended ASCII data can/cannot be transferred across platforms accurately

cannot

There are/are not enough codes to represent different languages in extended ASCII

are not

Unicode has become the universal ________

standard

Unicode is used by…

the major hardware and software manufacturers

Unicode can represent text in…

all known human languages

Unicode can use up to 32 bits to represent over…

1 million characters

True/False: The fist 128 characters of Unicode correspond to 7-bit ASCII

True

In pseudocode, programming languages have functions to return the ASCII code for characters in ______

denary

In a computer all images are represented as…

strings of 1s and 0s

pixel

Small points of colour that a digital image is composed of

What is pixel short for?

pixel element

Each pixel has its own individual ______

colour

The greater the number of pixels in a picture, the greater…

the detail in the picture

The size of an image is given as the number of…

pixels in its width and height

When a small image is enlarged to cover a large area it is…

less sharp

Why are small images less sharp when they are enlarged?

There are fewer pixels per unit area

What will happen to a small image when it is enlarged?

It will become blurred

If an image has fewer pixels per unit of area, it has a lower __________

resolution

What does the resolution of an image describe?

The number of pixels per unit area

Colour depth

The number of bits used to encode the colour of each pixel

In terms of colour depth - the more bits used to encode the colour, the greater the number of…

actual colours that can be represented in the image

What does the colour depth mean in terms of the quality of an image?

The higher the colour depth, the more detailed an image will be

Modern cameras and smartphones produce images with a colour depth of __-bits

The size of an image file in bits depends on… (give 2)

Image size and colour depth

How do we calculate the file size in bits of an image file?

Width x height x colour depth

The better the image quality, the ______ the file size

larger

When can large file sizes be a problem?

If they are being transferred electronically or storage space is limited

Metadata

extra information about the image stored within the file

Give 3 things that may be included in metadata

Any 3 from make and model number of the camera, dimensions of the image, file size, speed and apeture settings, GPS data showing the location where an image was taken, etc

Why should you take care when uploading images to social networking sites if GPS metadata is included in the file?

Strangers will be able to see your location

Sound can be represented in digital form as streams of…

1s and 0s

Sound is caused by…

vibrations travelling through a medium such as air, water or a metal

What do sound recordings convert?

Changes in air pressure into voltage changes

Sound recordings convert the changes in air pressure into volate changes. These are ________ recordings

analogue

Samples of the sound wave are taken at…

regular fixed intervals

Sampling frequency

When samples of the sound wave are taken at regular fixed intervals

A high sampling frequency gives a…

more accurate reproduction of the analogue wave form

Transistors are either __ or ___ and cannot continuously reproduce analogue changes

on or off

Digital recordings use _________ of the sound at regular fixed intervals and then play them back one after the other

snapshots

Samples

Snapshots of a sound at regular fixed intervals

A _______ _____ _________ is like an animated film that consists of many still images with tiny differences between them

digital sound recording

How is a digital sound recording like an animated film that consists of many still images with tiny differences between them?

When they are played back quickly it creates the illusion of movement

bit depth/sample size

Describes the number of bits used to encode each sample

A high bit depth allows more/less data to be stored and allows the dynamic range of the sound to be more/less accurately represented

more, more

True/False: In terms of bit depth, using 8 bits allows 255 graduations of volume

False, it allows 256

How does the fact that CDs are recorded in stereo and so have two channels impact the file size?

It will be doubled

Dynamic range

The range of volume in sound

What does the quality of digital audio depend on?

Sampling frequency and bit depth

The higher the sample frequency and bit depth, the larger/smaller the size of the audio file

larger

Bit rate

The amount of data processed every second

What is the equation for bit rate?

bit rate = sample frequency x bit depth

What is the equation for file size (bits)?

file size (bits) = sampling frequency x bit depth x recording length (seconds) or = bit rate x recording length (seconds)

How can the sizes of large files be reduced?

Using compression algorithms

What do compression algorithms do?

Repackage data or remove some of it

What does lossless compression do?

Reduces file sizes without deleting any data

True/False: With lossless compression, nothing is lost

True

How is data compressed with lossless compression?

Looks for redundancy where the same data is stored any times and groups this data into one reference

When is lossless compression commonly used?

Text files and graphic files with a low colour depth

Give an example of a less successful use of lossless compression

Audio files, 24-bit colour files

Compressed text files use lossless/lossy compression

lossless

GIF and PNG image files use lossless/lossy compression

lossless

FLAC and ALAC audio files use lossless/lossy compression

lossless

Why are FLAC and ALAC audio files becoming more popular on downloading websites for people who prioritise sound quality over small file size?

They can reduce the size of an uncompressed file by about 50%

What does FLAC stand for?

Free Lossless Audio Codec

What does ALAC stand for?

Apple Lossless Audio Codec

What does lossy compression do?

Reduces file size by deleting some data

When using lossy compression, the original can never/can be reconstituted - it has been irreversibly changed

can never

How is data compressed in image files with lossy compression?

Algorithms analyse the image and find areas where there are only slight differences - these are given the same value and the file can be rewitten using fewer bits

In lossy compression with image files, __________ analyse the image and find areas where there are only slight differences

algorithms

In lossy compression with image files, what happens once an algorithm has analysed the image and found areas where there are only slight differences?

These are given the same value and the file can be rewritten using fewer bits

How is data compressed in digital sound recordings with lossy compression?

Very small variations in frequency, tone and volume are removed to reduce the file size as the human ear cannot detect these small differences

In lossy compression with digital sound recordings, very small variations of what are removed?

Frequency, tone and volume

In lossy compression with digital sound recordings, why are very small variations of frequency, tone and volume removed?

To reduce file size as the human ear cannot detect these small differences

When is lossy compression commonly used?

Image files and digital sound recordings

When is lossy compression not used?

Text files

.mp3 audio files use lossless/lossy compression

lossy

.jpg image files use lossless/lossy compression

lossy

True/False: An MP3 file is usually about one tenth of the size of an uncompressed file, so more files can be stored on discs and SD cards

True

True/False: Billions of video, audio, multimedia and image files are uploaded and downloaded each day

True

Smaller file sizes make file transfer more _________

efficient

Smaller file sizes reduce the requirements for…

storage space

An advantage of compression is that more/less internet bandwidth is used when files are downloaded and uploaded

less

An advantage of compression is that transfer speed is slower/quicker

quicker

An advantage of compression is that more/less storage space is needed

less

An advantage of compression is that smaller/larger files reduce congestion on the internet

smaller

An advantage of compression is that ____ and _____ files can be streamed

audio and video

Give 3 advantages of file compression

Any 3 from less internet bandwidth is used when files are downloaded/uploaded, transfer speed is quicker, less storage space needed, smaller files reduce congestion and audio and video files can be streamed

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2.6 Data Representation COMPLETE Flashcards

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