Data Representation Flashcards
Explain why computers use binary.
Computers operate using logic gates, which have only 2 states, true and false
What is a computer made up of?
Billions of switches, which have an off (0) and on (1) position - this is called binary
How would you work out the number of possible combinations per switch?
You would do 2 to the power of n - with n being the number of switches
What are the units of data storage?
Bit - 0 or 1 Nibble - 4 bits Byte - 8 bits Kilobyte - 1000 bytes Megabyte - 1000 kB Gigabyte - 1000 MB Terabyte - 1000 GB Petabyte - 1000 TB
What are the rules in binary addition?
0 + 0 = 0
0 + 1 = 1
1 + 1 = 0 carry a 1
1 + 1 + 1 = 1 carry a 1
What is an overflow error?
When the result of adding two binary numbers is greater than the number of bits allowed
What is a binary shift?
A binary shift moves all of the bits in a given binary number either to the left or the right by a given number of places
What would a shift to the left do to a binary number?
multiply the number by 2 - you do 2 to the power of n (with n being the number of shifts)
What would a shift to the right do to a binary number?
It would divide the number by 2 - you would do 2 to the power of n (n being the number of shifts)
What is a character set?
A character set consists of all the letters, numbers and special characters that can be recognised by a computer system
How many characters does the ASCII character set include?
7 bits - 128 characters
How many characters does the Extended ASCII set include?
8 bits - 256 characters
How many characters does Unicode include?
16 bits - 65,536 characters
Explain one limitation of the ASCII character set.
➜ASCII uses only 7 bits so it can only represent 128 characters
➜which is not enough to represent other languages (e.g. Russian and Arabic)
What is a bitmap image?
A bitmap image is a digital image made up of pixels
What are pixels?
Pixels represent the smallest identifiable area of an image, each appearing as a square with a single colour
What is the colour/bit depth of an image?
its the number of bits per pixel
How do you figure out the bit/colour depth?
for example: 4 colours 4 = 2 to the power of 2 so the colour depth = 2 bit per pixel (the power is the bit depth)
What are the effects of increasing colour/bit depth of an image?
➜More colours can be represented so quality of the image increases.
➜However, this increases the file size
What is the resolution?
It is the density of pixels in the same area
What are the effects of more pixels per inch?
➜It will improve the overall quality
➜Which will increase file size
➜Which makes it possible to enlarge the image without visible loss of quality
What is metadata?
Metadata is the data stored in a file alongside the actual file data identifies
What are some examples of metadata?
➜Date created
➜File type
➜GPS location
What must analogue sounds be digitally recorded in?
binary
What is the amplitude?
the height of the wave
What is the frequency or sample rate of a wave?
How often the height is recorded
What is the sample resolution/ bit depth of a wave?
The accuracy to which the height is recorded - which impacts quality
What affects the file size for sound?
➜sample resolution
➜duration
What is sample rate measured in?
Hertz
What is the purpose of compression software?
Compression software uses algorithms to remove repeated or unnecessary data
What are the advantages of compression software?
➜Reduces file size
➜Reduces download time - as it is a smaller file
➜Uses less download data for users on a limited tariff (online downloads)
➜Reduces space on disk/server
Is a bitmap image compressed or uncompressed?
uncompressed
What is the ending for a bitmap image?
.bmp
What are some formats of lossy compression?
➜JPG
➜MP3
➜MPG
What are the advantages of lossy compression?
➜Smallest file sizes
➜Least transmission time (smaller file leads to fewer packets)
➜Reduces Internet traffic and collisions
What are the disadvantages of lossy compression?
➜Detail is permanently lost
What are the uses of lossy compression?
➜Music streaming
➜Online images and videos
➜Image libraries on devices or in the cloud
What are some formats of lossless compression?
➜PDF
➜GIF
➜PNG
➜ZIP
What are advantages of lossless compression?
➜Original quality is preserved - no information or data is lost
What are the disadvantages of lossless compression?
➜Less significant reduction in file size
What are some uses of lossless compression?
➜Text documents
➜Electronic books
➜High resolution print documents
What is decompression?
the process where compressed data is restored to its original format
What is the formula for calculating the size of an uncompressed music file?
Sample rate x bit depth x duration
What are lossy compression artefacts?
Noise at edges and blocks are digital artefacts from lossy compression
Are digital signals discrete or continuous?
discrete
