2.6 Data Representation COMPLETE Flashcards
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
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
What number system is binary?
Base 2:
2 possibilities - 1 or 0).
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.
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.
What is PPI and DPI?
Pixels per inch.
Dots per inch.
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.
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.
What happens with greater colour depth?
The more:
Realistic colours there are
Data needs to be stored.
File size on the disk is needed.
What happens with higher resolution?
There are more pixels, higher quality and higher image file size.
What is digital sound broken down into?
Thousands of samples per second - each of which are stored as binary data.
What does the quality of the samples depend on?
1) Sample frequency.
2) Sample size / bit depth.
3) Bit rate.
Define sample rate
No. of audio samples captured every second.
Define analogue
Made up of a variation of dynamic and frequencies.
Define sampling
Recording snippets of sounds at set intervals.
Define character set
The possible characters that can be represented in a computer system.
E.g. ASCII and Unicode.
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.
Define image size
Width and height of a bitmapped image, measured in pixels.
If an image has its colour depth increased what is the effect?
The file size is bigger.
Define overflow error
When the binary number is too big than actually possible
What are the hexadecimal numbers compared to denary numbers?
A = 10 B = 11 C = 12 D = 13 E = 14 F = 15
Define lossy compression
The file is compressed and data is lost. It compresses more than lossless
Should be used in audio files.
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.
What is the effect of multiplying the binary number by 2?
The number is shifted to the left by 1 bit
What is the effect of dividing a binary number by 2?
The number is shifted to the right by 1 bit
Define underflow
When the binary number is too small than actually possible
All data processed by a computer must be converted into ______ format
binary
A computer processor uses billions of ___________ acting as switches, which only act on the binary states on and off
transistors
All data and instructions in a computer are represented by…
the binary digits 1 (on) and 2 (off)
What binary digit represents ‘on’?
1
What binary digit represents ‘off’?
0
To be processed, instructions and data are converted to…
strings of 1s and 0s
Images and sounds must be _________ to be processed
digitised
What do inputs such as the keyboard and mouse send to the processor to be processed?
Combinations of 1s and 0s
One unit, either a 1 or a 0, is called a…
bit
What is bit short for?
Binary digit
True/False: More than one digit is needed to represent an item of data (such as a letter), in binary
True
True/False: Bits are organised into groups
True
4 bits = 1…
nibble
8 bits = 1…
byte
True/False: Bytes are grouped into small units
False, they are grouped into larger units
How many bytes are in a kilobyte?
1000
How many kilobytes are in a megabyte?
1000
How many megabytes are in a gigabyte?
1000
How many gigabytes are in a terabyte?
1000
How many terabytes are in a petabyte?
1000
What is the abbreviation for kilobyte?
KB
What is the abbreviation for megabyte?
MB
What is the abbreviation for gigabyte?
GB
What is the abbreviation for terabyte?
TB
What is the abbreviation for petabyte?
PB
How many bytes are there exactly in a kilobyte?
1024
When performing calculations, how many bytes do we say are in a kilobyte?
1000
The binary system is a base-_ number system
2
Why is the binary system a base-2 number system?
It uses two digits, 0 and 1
The denary system is a base-__ number system
10
Why is the denary system a base-10 number system?
It uses 10 digits, 0 to 9
The hexadecimal system is a base-__ number system
16
Why is the hexadecimal number system a base-16 number system?
It uses 16 digits, 0 to 15
In any system, the value associated with any digit is given by its…
place value
The value of each position in place value increases as the…
power of its base
What is the value of the 1st digit in an 8-bit binary number?
128
What is the value of the 2nd digit in an 8-bit binary number?
64
What is the value of the 3rd digit in an 8-bit binary number?
32
What is the value of the 4th digit in an 8-bit binary number?
16
What is the value of the 5th digit in an 8-bit binary number?
8
What is the value of the 6th digit in an 8-bit binary number?
4
What is the value of the 7th digit in an 8-bit binary number?
2
What is the value of the 8th digit in an 8-bit binary number?
1
What is 10 to the power of 7?
10,000,000
What is 10 to the power of 4?
10,000
True/False: You can convert denary numbers with values from 0 to 255 into 8 bit binary numbers
True
To convert numbers above 255 to binary, more ____ are required than 8 bit binary
bits
What are denary numbers also called?
Decimal numbers
Convert 234 to binary
11101010
Convert 42 to binary
00101010
Convert 87 to binary
01010111
Convert 67 to binary
01000011
Convert 12 to binary
00001100
Convert 6 to binary
00000110
Convert 124 to binary
01111100
Convert 183 to binary
10110111
Convert 132 to binary
10000100
Convert 245 to binary
11110101
How can you check you are correct in a denary to binary conversion?
By converting your binary number back into a denary number
True/False: Binary numbers can also be converted to denary numbers
True
What is 10001010 in denary?
138
What is 01011101 in denary?
93
What is 11010110 in denary?
214
What is 00011010 in denary?
26
What is 10100101 in denary?
165
What is 10101010 in denary?
170
What is 01010101 in denary?
85
What is 10010101 in denary?
149
What is 1 + 0 in binary addition?
1
What is 0 + 0 in binary addition?
0
What is 1 + 1 in binary addition?
10, you need to write the 0 and carry the 1 to the left
When do overflow errors occur?
When a calculation produces a result that is greater than the computer can deal with
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
16
Hexadecimal numbers need __ digits
16
There are no denary digits beyond _
9
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?
A
How is the denary number 11 represented in hexadecimal?
B
How is the denary number 12 represented in hexadecimal?
C
How is the denary number 13 represented in hexadecimal?
D
How is the denary number 14 represented in hexadecimal?
E
How is the denary number 15 represented in hexadecimal?
F
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
2
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
24
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
7
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
8
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
24
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
