U3 - Data representation Flashcards
What is the MSB
The most significant bit is the bit with the largest value (the bit that is furthest to the left)
What is the LSB
The least significant bit is the bit with the smallest value (the bit that is furthest to the right)
What is the largest number you can represent in 1 byte?
255 (but 256 numbers can be represented)
Advantages of hex (4)
- 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
Define overflow error
An overflow error occurs when the result of a binary addition is too large for the number of bits the computer works with
What effect does a binary shift left have on a number?
It doubles the number
What effect does a binary shift right twice have on a number?
It halves the number and rounds down each time
Define a character set
A set of letters, symbols and digits that can be represented by a computer
2 major character sets in use today
ASCII and unicode
How does ASCII encode characters?
It encodes 128 characters into 7-bit binary code
What is extended ASCII and how many characters can it encode?
Extended ASCII is an 8-bit character code to allow for many more characters to be represented e.g. copyright symbol. 256 different characters can be encoded
How does unicode encode characters?
It encodes 65,536 characters into 16-bit codes
What are bitmap images made up of?
Pixels
Define pixel
The smallest identifiable area of an image
How can a pixel’s colour change?
By changing the binary value of the colour
Define resolution
The concentration of pixels within a specific area
What happens when you have more bits per pixel?
More colour combinations
Bit depth in comparison to colour combinations examples
1 bit = 2 colours
2 bits = 4 colours
3 bits = 8 colours
4 bits = 16 colours
Higher bit depth
Gives a greater range of colour and a better quality of image
How does the number of colours affect file size?
An increase in the number of colours that are used in an image (the bit depth) will increase the file size
How does the size of the image affect file size? (2 meanings)
- An increase in the number of pixels in the image, will increase the file size
- If an images physical size is increased by making each pixel larger then there is no change in the file size
What does 0 and 1 correspond to?
0 = black 1 = white
What three colours does each pixel have a proportion of?
Red, green, blue
Why are colour values expressed as decimal RGB values and hex rather than binary?
RGB values and hex are easier for people to read, write and remember and reduce errors if copied
