Data Representation Flashcards
Nibble
4 bits
Byte (B)
8 bits
Kilobyte (kB)
1000 bytes
Megabyte (MB)
1000 kB
Gigabyte (GB)
1000 MB
Terabyte (TB)
1000 GB
Petabyte (PB)
1000 TB
why must data be stored in binary
the computer architecture is built on electrical transistors which can alternate between two states (1/0) very fast
sound file size
sample rate x duration (s) x bit depth
image file size
colour depth x image height x image width
text file size
bits per character x number of characters
binary base
base 2
how is an analogue sounds wave converted into digital form
the sounds wave is sampled by measuring the amplitude at regular intervals. The samples are stored and the data is converted into binary.
overflow error can lead to
loss of data and accuracy
over flow error
when the total from adding binary numbers is 9 or more bits which is too big to be stored within the registers of a CPU
most significant bit
the bit with the largest value (left-most)
least significant bit
the bit with the smallest value (right-most)
left binary shift
multiplies, every shift doubles the number
right binary shift
divides, every shift halves the number of
hex base
base 16
each hex character is equal to
a nibble in binary
character set
collections of characters that a computer recognises from their binary representation
character set egs
unicode, ASCII
how many characters can ASCII represent (each character is given a 7-bit binary code)
128 different characters
metadata
the aditional information stored in an image file which helps the computer recreate the image on screen from the binary data in each pixel
metadata eg
file format, width, colour depth, date
colour depth
number of bits used for each pixel
image resolution
the number of pixels in the image
increasing colour depth and resoultion
increases file size and quality of an image
sample rate
how many samples are taken in a second, measured in Hz
bit depth
the number of bits available for each sample
increasing sample rate or bit depth
increases the file size and improves the quality (closer quality to the original recording)
analogue sounds are stored in
binary
duration
how many seconds of audio the sound file contains
lossy compression
permanently removing data from the file
lossless compression
makes the file smaller temporarily by removing data, then restores it to its original state when opened
need for compression
-files take up less storage space
-downloading files is faster
-allows you to send the same content with a much smaller file size
lossy pros
-reduced file size
-takes up less bandwidth
-commonly used
lossy cons
-loses data permanently
-can’t be used on text or software files
-worse quality then the original
lossless pros
-no reduction in quality
-can be turned back to the original
-can be used on text and software files
lossless cons
only a slight reduction in file size
e.g of lossy file type
MP3, JPEG
e.g of lossless file type
PNG
