Data representation Flashcards
Why do computers use binary ?
- Computers only recognise one and zero
- It is à base to the number system
- incredibly efficient and effective way of storing information in a computer system
What does the bit pattern ‘01000111’ represent
- The binary number of 71
- ASCII character ‘G’
- a single pixel of colour in an 8-bit depth colour-depth bitmap
- part of a digital sound file
What does the decimal base system range from ?
0-9
what does the binary base system range from ?
1,0
What does hexadecimal range from ?
0-9 , and A-F
When we use binary left shift what does the bit multiply by ?
By a factor of 2
In binary right shift what does the number divide by ?
2
How many bits do characters(letters) take up?
128/7Bits
What is a character set?
A defined list of characters defined by the hardware and software
What does ASCII stand for ?
American Standard Code For Information Interchange
How many bits did ASCII have for character sets?
7Bits / 128
How many bits does extended ASCII have ?
8bits/256
Due to foreign languages and useful efficient graphic symbols
In ASCII what are characters 0-31 reserved for ?
Special characters and instructions for the computers
What is Unicode?
Used for all the languages and emojis
How many bit character set does Unicode have ?
24bit
However hexadecimal is used because 6digits in hexadecimal = 24 bits in binary .
Remember 1 nibble = 1hex digit
What is metadata ?
Additional data stored with the image such as width ,height ,colour depth of the image
In bitmap images not only does the metadata need to be stored but also …
The colour palette
How do you convert hex to decimal?
In hex moving right to left place values multiplied in powers of 16
To convert from decimal to hex divide by 16
How are images stored ?
As a series of pixels
What is the colour depth ?
The colour depth is the number of buts used for each pixel
How do you work out how many colours there are in an image ?
Total number of colours = 2(subscript)n (number of bits per pixel)
What is the image resolution ?
The image resolution is the number of pixels in the image. it sometimes given as width x height .The higher the resolution , the more pixels the image is made of , so the better quality of the image .
How to work out how many bits an image will take up
File Size=image resolution x colour depth x =width x height x colour depth
How is sound recorded as ?
Sound is recorded by a microphone as an analogue signal.
Analogie signals are piece of continuously changing data.
Analogue signals need to be converted into digital data so that computers can read and store sound files
Why might you want to compress data
- Smaller files take up less storage on a device
- streaming and downloading files from the internet is quicker as they take up less bandwidth
- allows web pages to load quicker
- email services have restrictions on the size of attachments you can send , thus compressing them permits you to send the same content but in a smaller size.
What are the differences between lossy and lossless compression?
- Lossy compression works by permanently removing data from the file , which essentially limits the bits the file needs and so reduces its size
- Lossless compression makes the file smaller by temporarily remo g the metadata and restoring it when the file is opened
Why might you want to use lossy compression?
- greatly reduced file sizes,meaning more files can be stored
- less bandwidth is required to stream
