(5) Data Representation Flashcards
What is natural numbers and its symbol?
All positive numbers whole numbers (integers) including zero
Symbol: N
What is integer numbers and its symbol?
All whole numbers including negatives and zero
Symbol: Z
What is rational numbers and its symbol?
Numbers that can be expressed as fractions
Symbol: Q
What is irrational numbers?
Numbers that cannot be expressed as a fraction
What is real numbers and its symbol?
Any number that isn’t infinity or imaginary
Symbol: R
What is ordinal numbers?
Numbers that can describe the position of an object
Why is hexadecimal used?
- Easy to represent a byte with two digits
- Easier for humans to remember
What is Unsigned and signed binary?
Signed binary - Binary values that can store both positive and negative values
(We use two’s compliment to represent this)
Unsigned binary - Binary values that can only store positive values
What are the advantages and disadvantages of fixed point(Signed Binary) and floating point(2s Complement) forms in terms of range, precision and speed of calculation?
Fixed point
+Allows for much faster processing compared to floating point numbers as no processing is required to move the binary point
+The absolute error will always remain the same, unlike floating point numbers
Floating point
+Wider range of numbers can be produced with the same number of bits as the floating point system
+
Why is floating point numbers normalised?
Allows the maximum possible precision with a given number of bits
Explain underflow and overflow and describe the circumstances in which they occur.
Overflow - When the number is too large for the number of bits allocated
Underflow - When the number is too small for the number of bits allocated
What is ASCII and Unicode?
ASCII - Represent a small range of 128 characters, uses 7/8 bits(1 including error checking digit)
Unicode - ASCII including alphabets for other languages and emojis, uses 16/32 bits
What is a parity bit?
An error checking digit used to check if the data has arrived correctly
There’s odd and even parity
What is majority voting?
Requires each bit to be sent three times. If a bit is flipped due to an error during transmission the computer would use the majority rule and assume the two bits unchanged where correct.
How does bit patterns represent bitmap graphics?
A bitmap image contains many pixels that make up the whole image. A pixel is the smallest element of a bitmap.
How does bit patterns represent sound?
This can be done by measuring and recording the amplitude of the sound wave, using a microphone, at given intervals. The more frequent the samples are taken, the more accurate the sound will be presented.
What’s the difference between analogue and digital?
Involving data and signals
Analogue data - Data that is infinitely variable and are often represented in the form of a wave
Digital data - Represented as discrete values
Describe the principles of an digital to analogue converter (DAC)
- convert binary into electrical energy
- that then vibrates the speaker
- that creates pressure waves which are the analogue sound
Describe the principles of an analogue to digital converter (ADC)
A microphone converts the sound energy to electrical energy. Regular samples are taken of the analogue signal at a given frequency, measuring the amplitude of the wave at each point and converting it into binary value according to the resolution or bit depth.
Explain how bitmaps are represented.*
An image made up of individual pixels, arranged as a grid
What is resolution for images?**
The number of pixels per inch
What is sample resolution?
The number of bits allocated to representing the sound
What is sampling rate?
Represents the number of samples that will be taken per second
What is colour depth?
The number of bits needed to stored each pixel
Advantages of normalised floating point format over fixed point format?
- To allow a wider range of values to be stored
- To minimise rounding errors
- Greater accuracy
What is metadata and what data might it contain?
Extra information about an image.
- Dimensions (h*w/ radius ect)
- Colour depth
- file type
- Gps coordinates
- Time and date of photo taken
What is the formula for pixel resolution?
resolution = height (in pixels) * width (in pixels)
What is vector graphics?
An image made up of objects and coordinates
Advantages of using vector graphics instead of bitmaps to represent an
image.
- less storage space required
- will load faster from secondary storage
- Will download faster
- Can be scaled / resized without distortion
What is Nyquist theorem?
In order to produce an accurate recording, the sampling rate must be at least doubled that of the highest frequency in the original signal.
The average human can hear frequencies up to 20,000Hz
How is sampled sound represented?
Sampled sound records measurements of (the amplitude) of a wave;
Samples are taken at regular intervals;
Each sample is stored in a fixed amount of memory; A. each sample is the same size
What is MIDI and a event messages and how is it represented?
A protocol that allows electronic instruments and other digital musical tools to communicate with each other.
Event messages specifies the pitch and duration of a note
MIDI represents sound as sequence of event messages // MIDI stores properties of the
notes played;
Advantages of using MIDI files for representing music over digital audio formats?
-MIDI files tend to be much smaller, therefore requiring less memory which leads to faster load times
-Completely editable
-Can support a wide range of instruments
Can produce very high quality reproduction of the instruments
What is RLE?
A simple form of data compression in which runs of data are stored as a single data value and count, rather than
as the original run
What is Lossless and lossy compression?
Lossless- When the data is compressed and uncompressed the data remains the same
Lossy- When the data is compressed and uncompressed some data is lost
What is encryption?
The process of making data unreadable for unauthorised access
What is the formula for the file size of sound?
Sample rate x Resolution x seconds
What is the formula for the file size of a bitmap image?
Number of pixels * colour depth
What is meant by a character code?
A character code uses a unique number to represent each different character
How to calculate the range of a given number of bits of 2^8?
find the biggest number and range of values you can have
2^8 = 256 values as you can also represent 0 2^8 = 255 is the biggest number that you can represent
What base is decimal, binary and hexadecimal?
Decimal - 10
Binary - 2
Hexadecimal - 16
Describe sampled sound:
- Sampled sound records measurements of the amplitude of a wave
- Samples are taken at regular intervals
- Each sample is stored in a fixed amount of memory
Explain why both fixed point and floating point representation of decimal numbers may be inaccurate?
They both have rounding errors
