1.3 Data Storage Flashcards
how are fractions stored in binary
for example a quarter which is 0.25 is stored in binary as 25 with an extra byte to store the position of the decimal point “.”
how is text stored and processed in a computer
every character, upper or lowercase including punctation is stored with a number code, this character code usually is ASCII but has been improved to unicode
what does ASCII stand for
American Standard Code for Information Interchange
why are there file types
different ways of storing digital data are called formats, different types of files use different data formats
what is a file extension
3 or 4 letters after the full stop of a file name to show the data type stored in the file
give some examples of file types
.txt means file holds text stored in ASCII code
.doc means file holds text + document formatting
.exe means file holds instructions which the computer can carry out, execute
why do different file types require software to open the file
all files uses binary however the numbers in different file types mean different things, the computer must detect the file type so it knows what the binary represents, in some cases you need a software to open a file format
what does a bitmap file store
it stores the position of every pixel and its colour that makes up an image
why are bitmap files so large
because bitmap files contain the position and colour of everypixel in a number code, the full dot by dot detail
how do vector files store data
by storing the mathematical formula of how to draw the lines and shapes in an image
why are vector graphics not good for photographs
because they store the mathematical formula for lines and shapes, they are not good for intricatly detailed photographs, they are good for clipart or cartoons
what is high and low resolution
the resolution of the image depends on how many pixels and the size of them in an image. lots of small pixels is high
what is pixelation
if an image is made larger, the pixels are get larger and the resolution decrease, we say that this image is pixelated
why are vector graphics not affected by pixelation
because vector graphics store the mathematical formula on how to draw the shapes and lines in an image, so they can adjust to the screen resolution when you zoom in
what is colour depth
the amount of colours that can be used in an image
give some examples of different colour formats
monochrome - black or white so 0 or 1
16- colour, each pixel is half a byte
156 colour, each pixel is a byte
what are the 3 different types of sound formats
WAV file, MP3 and MIDI
why is compression used
to reduce the size of a file for it to take less space or send quicker
what is lossy compression
compression which reduces the size of the file by using algorithms that reduce the data quality such as image quality, some data is purely lost
what is lossless compression
reduces the file size however no loss of data quality
give an example of lossless compression
an image where a particular colour is recurring greatly, a byte will be used to store the colour and other bytes will be used to store the amount of the colour before it changes in each row, this will be less data than storing the position of each and every white pixel, this compression works good on cartoon or clipart images, images with high detail cannot work well with this
give an example of why certain file formats have to be compressed a certain way
for example an .exe file where it stores instruction for the pc, cannot be compressed lossy, because we cannot afford to lose a singal command
what are the features of lossy compression (4)
some data is lost
greatly reduces the size of the file
reduces quality of sound/image
cannot be used with text or executable files
what are the features of lossless
no data is lost, just encoded differently
files are recovered to their original state
can be used with all file formats
less effective at reducing file size than lossy
