Information Representation Flashcards
Denary Definition
base-10 number system that uses values 0-9 to represent each digit.
Hexadecimal definition
base-16 number system that uses values 0-9 and characters A-F
3 advantages of hexadecimal
*Easy to read, write and understand.
*Shorter way of representing binary
*Easier to debug and locate errors in data.
Name 3 ways in which hexadecimal is used
*Define locations in memory
*Colour values
*MAC addresses
Binary definition
base-2 number system that uses values 0 and 1.
Bit definition
a digit expressed using either 0 or 1 in a binary number system.
Byte definition
a group of eight bits treated as a single unit.
Nibble definition
a group of four bits.
Binary prefix definition
A prefix to define the magnitude of a value. E.g., Kibi, mebi, gibi and tebi representing factors 2^10, 2^20, 2^30 and 2^40 respectively.
How much is one kibibyte?
1024 bytes
How much is one kilobyte?
1000 bytes
Decimal prefix definition
A prefix to define the magnitude of a value. E.g., Kilo, mega, giga, and tera representing factors of 10^3, 10^6, 10^9 and 10^12 respectively.
Binary Coded Decimal definition
storage of a binary value representing one denary digit in a nibble.
Where is BCD used?
Used in:
screen on a calculator
digital time display
Representation of currency values
Bar codes
Packed BCD definition
two BCD nibbles stored in one byte
Overflow definition
a condition when the result of a calculation is too large to fit into the number of bits defined for storage.
How many codes could original 7-bit ASCII store?
128
Who was ASCII standardised by?
American National Standards Institute (ANSI)
What are non-printing or control characters
introduced in ASCII to help in data transmission or data handling at computer terminals
For which bit do the uppercase letter codes differ from the lowercase in ASCII?
The 5th bit
Standardised version of Extended ASCII and what does it include
ISO Latin-1. Accented/modified alphabets. up to 256 codes.
What was unicode developed alongside?
Universal character Set UCS scheme
What is the most popular version of unicode?
UTF-8
Which unicode codes are the same as ASCII?
First 128
What is a character code called in unicode and how is it documented
Code point
U+ 4-digit hexadecimal number.
What is a vector graphic?
a computer image consisting of drawing objects defined in a drawing list
What is vector image created by?
drawing package or computer-aided design (CAD) package
Drawing list definition
contains one set of values for each drawing object. (command (containing list of attributes defining a property) required to draw each object)
Drawing object definition
a component defined by geometric formulae and associated properties.
Define property and list 6 of them
defines one aspect of the appearance of the drawing object.
- Position
- Radius
- Line style
- Line width
- Line colour
- Fill colour
How are dimensions of objects defined in a vector image?
relative to an imaginary drawing canvas.
Image is scalable.
This avoids image distortion.
What can vectors only be displayed on?
graph plotter
What does the SVG format use?
XML-based text format to describe how the image should look
How are bitmaps stored?
2-dimensional matrix of pixels
What is a pixel and how is it defined?
smallest identifiable component of a bitmap image, defined by two properties - position in the bitmap matrix - colour
Image resolution definition
number of pixels in the bitmap file defined as the product of the width and height values
Screen resolution definition
product of the width and height values for the number of pixels that the screen can display.
Colour depth definition
number of bits that are used to create each colour in an image. (represent one pixel) 16-bit, etc. SQUARED
Bit depth definition
number of bits used to represent each of the red, green and blue colors. Cubed
Pixel density definition and how to calculate it
number of pixels per square inch.
1. Add together squares of resolution size
2. Find square root.
3. Divide by screen size
What is a file header?
set of bytes at the beginning of the bitmap file which identifies the file and contains information about the coding used.
- Width and height measured in pixels
- date stamp
- image resolution
- Bit depth
- Data compression
How is sound transmitted?
by causing oscillations of particles within the medium
How is sound converted to digital data
measured sound values being put into sound encoder which has a band-limiting feature to remove high frequencies and then to ADC converter
What is determined when turning sound to digital data?
Amplitude
Analogue data definition
data obtained by measurement of a physical property which can have any value from a continuous range of values.
Digital data definition
data that has been stored as a binary value which can have one of a discrete range of values.
Sampling definition
taking measurements at regular intervals and storing the value
Sampling rate definition
the number of samples recorded each second.
Sampling resolution definition
the number of bits used to record each sound sample. E.g., 16-bit
Pros and cons of larger sampling resolution
Pros
- Larger dynamic range
- Better sound quality
- Less sound distortion
Cons:
- Takes longer to transmit
- Greater processing power
- Larger file size
Abilities of sound editing software
-Edit start/stop times and duration
-Alter frequency and amplitude of a sample
-Extract and save/delete part of a sample
-Fade in/out
-Mix and/or merge multiple soundtracks
Describe how video is digitalised
Camera picks up light from the image and turns it into an electronic signal using light-sensitive sensors. DV cameras signals automatically converted into compressed digital format.
Lossless compression definition
coding technique that allows subsequent decoding to recreate exactly the original file.
Lossy compression definition
coding technique that causes some information to be lost so that the exact original file cannot be recovered in subsequent decoding.
Describe Huffman encoding
Lossless: text is analysed to find the most often used characters which are then given shorter codes. Original stream of bytes becomes a bit stream. Stored in a translation table. Can also compress sound file which is more effective as some values for amplitude occur far more often than others.
Describe Run-length encoding
Lossless file compression technique to reduce text and photo files. Reduces size of string of adjacent, identical data by:
- Repeated string encoded into two values: number of identical data items and code of the data item
- Only effective when there is a long run of repeated units.
What is JPEG?
Joint Photographic Expert Group: form of lossy file compression based on inability of the eye to spot certain colour changes and hues. Reduces raw bitmap image by factor of 5-15
What is MP3/MP4?
file compression for music and multimedia files.
How to reduce the file size of movie files?
reduce sample resolution/rate and frame rate
How to reduce the file size of image files?
Crop, decrease colour depth, reduce image resolution
What is a multimedia container format?
A metafile containing both audio and video that describes how the encoded data is stored.
What is perceptual music shaping?
a process that is used in lossy compression that removes sounds that are not normally heard by the human ear.
What is spatial redundancy?
when a sequence of consecutive pixels in the same frame have the same value.
