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
what is the correlation between the colours an image requires and bit depth (bits per pixel). what does this result in and why? (2)
- the more colours an image requires, the more bits per pixel are needed.
- a larger file size as more data is stored
what does higher resolution result in? and why?
a bigger file size as more data is stored
characteristics of a low resolution image: (2)
- has less pixels, which means that the pixels are larger and therefore, fewer are needed to fill the space.
- this results in images that look blocky or pixelated (an image of lower quality)
characteristics of a high resolution image: (2)
- has more pixels, which means that the pixels are smaller and can provide a more accurate depiction of the image (as they can display all minute details-including the full range of colours-visible to the naked eye)
- this results in the image appearing to be of higher quality, irrespective of whether it is enlarged or stretched.
which factors affect the quality and size of an image?
resolution and colour depth
what happens when colour depth and resolution are increased? and vice versa? (2)
increased: relative quality of image increases, but so does file size
decreased: relative quality of image decreases, but so does file size