Topic 1-Data Representation Flashcards
1 Byte(B) equals to
8 bits(b)
Bit
one binary digit
Nibble
4 bits
Byte
8 bits
Word
16/32/64 bits
Kilobye(KB)
1024 bytes
Megabyte(MB)
1024 KB
GIgabyte(GB)
1024 MB
Terabyte(TB)
1024 GB
Petabyte(PB)
1024 TB
0+0=
0
1+0=
1
0+1=
1
1+1=
0, carry the 1 to the left
1+1+1=
1, carry the 1 to the left
1010+1001=
10011
101101+111101=
1101010
What number system do these facts describe: 0 or 1(2 digits) - base 2 - Used by computers - Uses more digits for the same number
Binary
Name 4 facts about the denary number system
0, 1, 2, 3, 4, 5, 6, 7, 8, 9(10 digits) - Base 10 - Used by humans - Uses less digits for the same number
a bit is either a _ or a _
1 or 0
Binary digit can be shortened to
bit
The smallest piece of computer memory is
a bit
A single 1 or 0 is called a
bit
Computers convert ____ data to ____ data
analogue to digital
How many megabytes in a gigabyte?
1024 MB
what comes after Kilobyte?
megabyte
One Byte can store a single ___
character
?
?
32
16
8
?
2
?
1, 4, 64, 128
0+0+0=
carry 0, sum 0
0+0+1=
carry 0, sum 1
0+1+0=
carry 0, sum 1
0+1+1=
carry 1, sum 0
1+0+0=
carry 0, sum 1
1+0+1=
carry 1, sum 0
1+1+0=
carry 1, sum 0
What is the logical (binary) shift?
Moving the binary number to the left/right. Each shift left is equivalent to multiplying the binary number by 2 and each shift right is equivalent to dividing the binary number by 2.
10010101 in a denary number
149
how to convert from denary to binary
- keep dividing by 2
- use INTEGERS only
- write down the REMAINDERS
- write the remainders from BOTTOM to TOP
177 in a binary number
10110001
what is two’s complement for?
to convert negative denary numbers
name 4 facts about the hexadecimal system
0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A(10), B(11), C(12), D(13), E(14), F(15) (16 digits) - Base 16 - FOUR binary digits are equivalent to each hexadecimal digit
1 1 1 1 =
F, 15
0 1 0 0 =
4, 4
how to convert from Binary to Hexadecimal:
- from RIGHT to LEFT, split the binary into groups of 4 BITS.
- write BASE 2 headings(8, 4, 2, 1) for each group of bits.
- work out the DECIMAL value for each group.
- replace any value above 9 with its HEX code.
1011010101 in HEX code=
2D5
how to convert from Hexadecimal to Denary:
- write the Base 16 headings(256, 16, 1).
- Multiply out(HEADING x HEX code).
define MEMORY DUMP
when the memory contents are output to a printer or monitor
why might a programmer prefer to use hexadecimal to ss the contents of locations?
- easier to identify values
- easier to spot errors
MAC address stands for
Media Access Control; refers to a number that uniquely identifies a device on the internet; usually made up of 48 bits(6 groups of hexadecimal digits)
What does the first half of a MAC address identify?
the manufacturer
What does the second half of a MAC address identify?
the serial number of the hardware
one type of MAC address
UAA(Universally Administered MAC Address); by far the most COMMON type of MAC address; set by the manufacturer
another type of MAC address
LAA(Locally Administered MAC Address)
3 facts about a MAC address
- on mainframe systems all MAC addresses of devices may need to fall into a strict format
- to bypass a MAC address filter on a router/firewall
- to get past certain types of network restrictions it may be necessary to emulate unrestricted MAC addresses
IP address stands for
Internet Protocol
An IPv4 address is a ___-bit number written in ____ or _____ form
32, denary, hexadecimal - IPv4 has recently been improved upon by the adoption of IPv6.
An IPv6 address is a ___-bit number broken down into ____-bit chunks, represented by a _____ number.
128, 16, hexadecimal
An IPv6 address is a ___-bit number broken down into ____-bit chunks, represented by a _____ number.
128, 16, hexadecimal
HTML Colour Codes
- every pixel in a computer colour monitor may have only ONE COLOUR at any moment
- each made up of a combination of RED, GREEN, and BLUE
- hexadecimal RGB colour values that specify the AMOUNT of red, green, and blue light that need to appear at a pixel, in order to produce a specific colour
- each colour value is represented as a HEXADECIMAL value of 2 digits that may take up values from 00 to FF.
the first 2 digits of HTML Colour Codes represent the ____ colour, the next 2 the ____ colour, and the last 2 the ____ colour.
Red, Green, Blue
ASCII code stands for
The American Standard Code for Information Interchange
What is an ASCII code?
a character-encoding scheme originally based on the English alphabet; a number is assigned to each letter from 0~127 in denary or 0 to 7F in hexadecimal; 32 control codes(that use codes O to 31(denary) or 00 to 19(hexadecimal))
ASCII uses 7 bits to represent each character which means that it can achieve 27=128 different representations
x-axis in representation of sound shows:
the TIME INTERVALS when the sound was sampled(1 to 21); At time interval 1, the approximate amplitude is 10. At time interval 2, the approximate amplitude is 4.
y-axis in representation of sound shows:
the AMPLITUDE of the sampled sound to 10
What is a sampling resolution(aka the bit depth)?
the number of bits per sample
What is a sampling rate?
the number of sound samples taken per second. Measured in hertz(Hz), where 1 Hz means ‘1 sample per second’.
How is sampling used to record a sound clip?
- the amplitude of the sound wave is first determined at set time intervals (the sampling rate).
- this gives an approximate representation of the sound wave.
- each sample of the sound wave is then encoded as a series of binary digits.
Using a _____ sampling rate/____ resolution will result in a more _____ representation of the original sound source. However, the _____ the sampling rate/sampling resolution, the _____ the file size.
higher, larger, faithful, higher, greater
Benefits of using a LARGER SAMPLING RESOLUTION when recording sound
larger dynamic range; better sound quality; less sound distortion
Drawbacks of using a LARGER SAMPLING RESOLUTION when recording sound
produces larger file size; takes longer to transmit/download music files; requires greater processing power
What are bitmap images?
made up of PIXELS(picture elements); an image is made up of a 2-DIMENSIONAL MATRIX of pixels; pixels can take DIFFERENT shapes
representation of (bitmap) images: Each _____ can be represented as a ____ number, and so a bitmap image is stored in a computer as a series of ______ numbers so that a ____ and ____ image only requires 1 bit per pixel 0 - this means that each pixel can be one of two colours, corresponding to either __ or __. If each pixel is represented by __ bits, then each pixel can be one of four colours(22=4), corresponding to [ ]. If each pixel is represented by __ bits then each pixel can be one of eight colours (23=8), corresponding to 000, 001, 010, 011, 100, 101, 110, 111.
pixel, binary, binary, black, white, 1, 0, 2, [00, 01, 10, or 11]
define colour depth
The number of bits used to represent each colour; increasing colour depth also increases the size of the file when storing an image.
define Image resolution
the number of pixels that make up an image; the resolution can be varied on many cameras before taking
Photographs with a ____ resolution have ____ less detail than those with a ____ resolution.
lower, less, higher
What does resolution measure?
the number of pixels in a digital image/display; defined as width by height
The file size of an image is determined by:
the number of pixels
The file size of an image is determined by:
the number of pixels
memory size is measured in terms of powers of:
2
file size(of an image) formula
image resolution(in pixels) x colour depth(in bits)
size of a mono sound file formula
sample rate(in Hz) x sample resolution(in bits) x length of sample(in seconds)
stereo sound file formula
2 x [sample rate(in Hz) x sample resolution(in bits) x length of sample(in seconds)]
In ASCII code each character from the keyboard has a value of __ byte.
1
Benefits of data compression
- save storage space on devices such as hard disk drive/solid state drive
- reduce the TIME taken to STREAM a music/video file
- reduce the time taken to UPLOAD, DOWNLOAD, or TRANSFER a file across a network
- reduced file size also reduces COSTS
2 types of file compression
Losy or Lossless
File compression is enabled through a ___ or ____ compression software that creates a _____ version of each processed file
file, data, compressed
Lossless file compression
all data bits from the original file are RECONSTRUCTED when the file is again uncompressed
In what cases are Lossless file compression crucial?
Files where loss of any data would be disastrous. E.g. a spreadsheet file.
OR
where code must be exactly the same as the original. E.g. computer program
Features of Lossless compression
- If the code different from the original, the file won’t work
- an algorithm used
- no data removed in the process
- in a text file repeated words are identified/replaced by an index
- the number of times the word appears is stored
Lossy file compression
the compression algorithm eliminates unnecessary bits of data as seen in MP3 and jpeg formats; IMPOSSIBLE to get the original file back
When is Lossy file compression mostly used?
In compression of files where removing certain bits doesn’t detract from the quality. E.g. Video file
Features of Lossy compression
- makes the file SMALLER than lossless
- quality REDUCED but the file still RUNS
- REDUNDANT amount can be removed
MIDI stands for
Musical Instrument Digital Interface
MIDI files are not ____ and don’t contain any ____
music, sounds
What is a MIDI file?
a communications protocol that allows electronic musical instruments to interact with each other.
The MIDI protocol uses __-bit serial transmission with one start bit and one ___ bit; asynchronous
8, stop
A MIDI file consists of a list of _____ that instruct a device how to produce a particular ____ or _______.
commands, sound, musical note
MIDI file size
bc MIDI files don’t contain any audio tracks, their size is considerably smaller compared with an MP3 file; makes them ideal for devices where memory is an issue E.g. storing ring tones on a mobile phone
Mp3(MPEG-3) uses:
audio compression to convert music/other sounds into an Mp3 file format.
Audio compression reduce the size of a normal music file by about ____ per cent.
90
Bit rate
the number of bits per second
Mp3 files use ___ format bc part of the original file is lost following the _______.
lossy, compression algorithm.
What technique is used in Mp3 files?
PERCEPTUAL MUSIC SHAPING - removes sounds the human ear CANNOT detect; where two sounds are played SIMULTANEOUSLY the softer sound is REMOVED
Mp3 is a digital recording of sound whilst MIDI is a
non-audio recording
MIDI is produced by synthesizer whilst Mp3 is produced by
recording software
difference between Mp3 and MIDI
MIDI is an instruction of how to make sound
Mp3 is a compressed file format whilst MIDI file is created using
digital musical instruments
Mp4(MPEG-4) allows the storage of
multimedia files(music, videos, photos) rather than just sound.
define Image Compression
When a photographic file undergoes file compression, the size of the file is reduced.
image compression - TIFF and BMP are the highest image quality because
unlike jpeg, they’re not in a compressed format.
JPEG
another example of LOSSY file compression; reduce the RAW BITMP image by a factor of between 5 and 15 depending on the original quality.
JPEG relies on certain properties of the ____ and, up to a point, a certain amount of file compression can take place without any real ____ of quality.
human eye, loss
RLE stands for
Run-length Encoding
What type of compression is used in RLE?
lossless(reversible)
Features of RLE
- Reduces the size of a string of adjacent, identical data
- RLE is only effective where there is a long run of REPEATED units/bits.
What does the first value represent in a repeating string encoded into two values in a RLE?
The number of identical data items in the run.
What does the second value represent in a repeating string encoded into two values in a RLE?
The code of the data item(such as ASCII code if it is a keyboard character).
What is a FLAG in RLE?
a flag preceding data indicates that what follows are the number of repeating units
What happens when a flag is not used in RLE?
the next bytes are taken with their face value and a run of 1.
