1.2: MEMORY AND STORAGE 3.0 Flashcards
explain the effects of performing a 2 place right shift on a binary number:
- divide by 4
- loss of accuracy/ precision (bits on the right are removed)
What is the purpose of data compression?
-reduces the size of a file stored on secondary storage.
Advantages of data compression: (2)
- smaller files are easier to transmit across a network as they require fewer packets to be sent.
- their reduced size means more files can be stored in the given area of storage.
What are the two types of compression?
- lossy compression
- lossless compression
What happens with lossy compression? and what does it result in?
Lossy compression standards (file formats):
- some data is removed and discarded, thereby reducing the overall amount of data and the size of the file.
- JPEG, MPEG, MP3
What happens with lossless compression?
lossless compression standards (file formats):
- files are reduced in size without the loss of data
- PDF (text documents), GIF (image file format)
Give an example of how lossy compression can affect the quality of a file:
-reduction of colour depth in a JPEG image
what does a character set (as a group) assign? and what does it enable the computer to do (2)
- group of code that assign a character to a unique bit pattern,
- which enables the computer to understand and display it
what does a character set consist of?
-all the letters, numbers and special characters that can be recognised by a computer system
2 common character sets:
- ASCII
- Unicode
what does ASCII use and what does it provide?
- 8 bits
- character set of 256 characters
what is a possible problem that might be encountered with ASCII?
-256 characters is far too small to hold every character in other languages or contain custom characters
what does Unicode use and what does it provide?
- 16 bits
- character set of 65,536 characters
what does Unicode use that makes it more efficient?
what could Unicode’s larger character set be used to represent?
- uses more bits, thereby providing a larger character set
- characters from foreign languages and custom characters
how are character sets ordered?
logically
what is the number of characters stored limited by?
of bits available
what is a bitmap? and what happens to it when it is scaled up? (2)
- image made of pixels
- it blurs when scaled up
what are digital images made up of?
pixels.
what is ‘pixel’ short for? what does each pixel have? and what is it encoded in?
- picture element
- each pixel has a single colour which is encoded in binary.
what is each pixel represented by?
a binary number.
what does the number of bits determine? (in an image)
-the range of colours.
what is resolution? and what is it expressed as?
what is resolution a measure of?
- number of pixels that an image contains
- height and width
-how tightly packed the pixels are.
Describe how bitmap images are represented in binary: (3)
- image is composed of/ split up into pixels.
- each pixel is encoded with a binary code which represents the colour of that pixel.
- each colour is assigned a unique bit pattern.
what is colour depth?
bits per pixel used to represent a colour
