2b) Data Representation And Memory Flashcards
How much is a nibble?
4 bits
How much is a byte?
8 bits
How much is a kilobyte?
1000 bytes or 1Kilobyte
How much is a megabyte?
1000 KB
How much is gigabyte?
1000 mb
How much is a terabyte?
1000 Giga byte
How much is a petabyte?
1000 TB
What does data need to be converted in?
Data needs to be converted in binary so a computer can understand it.
What is binary used to store?
Numbers,text,images, sound and program instructions
Why should data be stored in binary format?
Computers can only understand on and off switch circuits which are represented as 1s and 0s in binary. Circuits only need to check for two states.
How do you find the size of sound?
Sound file size = sample rate x duration (s) x bit depth
How do you find image file size?
Image file size = colour depth x image height (px) x image width (px)
How do you find text file size?
Text file size = bits per character x number of characters
How to convert denary to binary?
128,64,32,16,8,4,2,1
What is a binary overflow error?
When adding two binary numbers we can end up with an extra digit that doesn’t fit.
What are the Hexadecimal digits?
1 2 3 4 5 6 7 8 9 A B C D E F
How to convert denary to Hex?
First draw the hexadecimal digits. Then Divide the number by 16 and write the digit then use the chart and put the remainder ad well.
How to convert binary to hexadecimal?
First split it up in 4s. Then 8421 above both 4 numbers. Find the numbers out and convert to hexadecimal.
What is most significant bit?
Th number furthest to left ( can be 0 or 1)
What is least significant bit?
Number furthest to the right ( can be 1 or 0)
What is binary shift?
moving the binary digits in the accumulator to the left or right a given number of spaces.
How are characters are represented in binary?
By ASCII they charcters on a keyboard are assigned to a binary number
How are characters represented?
Using binary codes
What are character sets and what are the major ones we use today?
Character sets are a set of letters,symbols and digits that can be represented by a computer
- ASCII
- UNICODE
The relationship between the number of bits per character in a character set, and the number of characters which can be represented?
• The more bits per character in a character set the more characters which can be represented
For example:
• ASCII = 7-bits - 128 characters
• Extended ASCII = 8-bits - 256 characters
• UNICODE = 16-bit and 32-bits - every possible character which might be written
How is an image represented?
As a series of pixels, represented in binary
What is a pixel?
The smallest part of an image
What does each pixel specifically have?
A specific colour and represented by a specific code
What is meta data?
Meta data is data about data for example :
- Author
- Date created
- Resolution
- Colour depth in bits per pixel
- height, width
What does a higher bit depth give?
A bigger range of colours
If 8 bits per pixel
2^8 = 256 colours
2^16 = 65,536
The effect on image size and quality when changing colour depth and resolution
The more colours larger the file size will be
How sound can be sampled and stored in digital form?
An Analogue to Digital Convertor (ADC) is used to
convert inputs to digital signals
How are analogue sounds stored?
In binary
What are sample rates measured in?
Hertz
What is bit depth in sound?
Number of bits to store each sample
What is sample rate?
The sample rate is the number of samples taken
per second
What does more bits in sound do?
Enables the height of the wave to be accurately measured but increases file size
What is the need for compression?
Reduces the storage size
Reduces download times
Music and video is streamed faster
Where is compression needed ?
Communication bandwith
reduces size of am image
Send photos and videos faster
What are disadvantages of lossy?
- Loses some data
- Blocks can often result from lossy compression
- Noise can be often seem where there are contrasting colours
Lossless advantages?
- will not lose any data
- The algorithm finds groups of repeating data and records the
data once along with the number of repetitions - When data is uncompressed it is restored exactly as
it was in the original
Disadvantage of lossless
- larger than lossy files
- May impact speed
Advantages of lossy?
Small file sizes. Ideal for web use. Lots of tools, plugins and software support it.
