Unit 2 - Data Representation✔️ Flashcards
How many bits in a byte?
8 bits
How many bytes in a kilobyte?
1000 bytes
How many megabytes in a gigabyte?
1000 megabytes
What is a hexadecimal?
• Hexadecimal (or hex) is a number system which uses base 16
Advantages of using hex rather than binary?
• It is much simpler to remember a hex value than a binary value
• It is quicker to write or type since a hex digit only takes up one digit rather than 4 bits
• People are less likely to make an error with fewer digits
• It is easy to convert between hex and binary
What is an overflow and how it is caused?
• When the result of an addition is too large for the number of bits the computer works with there will be an overflow error
What hapens with a binary shift?
• A binary shift moves all the bits one place to the left or right
What is a character set?
• All of the characters that a computer can use are called a character set .
What are the two major character sets?
• ASCII
• Unicode
What is ASCII?
• ASCII (American Standard Code for Information Interchange) has become the standard code, used worldwide
How many bits are used in extended ASCLL to represent a character?
8 bits
How many characters does ASCLL allow for?
256
How many combinations with 16 bit unicode?
65,536 possible combinations
How many combinations with 32 bit verion?
4,294,296 possible combinations
Example of Bitmap file formats?
-JPG
-GIF
-PNG
Define a pixel?
Pixel is the smallest identificable area of an image - each pixel is a single colour and is given a binary value which repersents that colour
What is each pixel given in an image?
A single colour repersented by a binary value
What is resolution?
Is the concentration of pixels within a specific area
*Area defined by the image width and height in pixels eg 1920 x 1080
How many colours combinations with 1 bit?
1 bit = 2 colours
2 bit = 4 colours
3 bit = 8 colours
4 bit = 16 colours
What will a higher bit depth result in?
• A higher bit depth gives a greater range of colour and a better quality of image
What is megadata and what does it contain?
• It is information other than image data that is stored with a file
•includes
-colour depth
-resolution
-date created
-author
What is a result of greater resolution?
Greater file size
What is used to convert inputs to digital signals?
Analogue to digital convertor (ADC)
What is used to convert signals to outputs?
Digital audio convertor (DAC)
Why are sounds converted to digital form?
• Sounds must be converted into a digital form in order to be stored and processed by a computer
What is the sample rate?
• The sample rate is the number of samples taken per second
• It is measured in hertz (Hz)
What is a sound sample?
• A sound sample is a measurement of amplitude of a sound wave at a given time and
How is sound sample?
• Sound is sampled using a bit depth and sample rate
• The bit depth determines how closely the wave is sampled on the y-axis
What is a sounds resolution?
• The number of bits (audio bit depth) used to record each measurement is known as the resolution
• More bits used per sample enables the height of the wave to be more accurately measured but increases file
How many samples per a second is 1 Hz ?
1 Hz = 1 sample per second
Effect of frequency on sampling rate?
• The frequency or sample rate per second affects the level of detail in the digital representation
• The greater the frequency, the greater the accuracy, and file size
Equation for files size?
File size (bits) = sample rate x bit depth x duration
What is lossy compression?
• Lossy compression removes sounds that we can’t easily hear and will not affect quality
Issue of lossy compression on sounds?
• Lossy compression leaves out some data from the original so can negatively affect the sound quality
-requires a larger uncompressed WAV file
Benefit of lossy compression on sounds?
• This is useful for storing, downloading or streaming
What is lossless compression?
• Lossless compression formats are able to reduce the file size when compressed but do not lose any information
Three examples of lossless music file formats?
•FLAC
•ALAC
•WMA lossless
Define a sounds bit depth?
• The number of bits available to store each sample is known as bit depth
What is compression?
• Compression is the name given to algorithms which reduce file sizes
• used heavly with sound,image and video files
What is decompression?
• Decompression is the process where compressed data is restored to its original format
Give the two examples of compression?
• Lossy compression (JPG, GIF, MP3)
• Lossless compression (PNG, TIFF)
Main issues with lossy compression?
• Lossy compression permanently loses some data
• Lossy compression results in small mistakes known as ‘digital artefacts’
Main benefit with lossless compression?
• Lossless image compression will not lose any of the original data
How does lossless compression work?
1)finds patterns in the original text
2)encodes each pattern in a dictionary
Why are files and data sent via the internet normally compressed?
• Download times are reduced
• Data allowances go further
• It is possible to transmit video and music data
streams as fast as they are playing
Benefits of compression?
• fewer packets because there are fewer packets
• Quicker to complete transmission
• Reduces traffic over the Internet
• Images inside web pages appear faster
• Reduces space on disk / servers
What causes buffering?
• Video or music streaming causes buffering if the download speed is slower than the playback speed
