Data representation (Paper 1 & 2) Flashcards
Why is hexadecimal often used?
It’s easier for humans to remember hexadecimal numbers as opposed to binary numbers
How many bits in a byte?
8 bits = 1 byte
How many bytes in a kilobyte?
1000 bytes = 1 kilobytes
How many kilobytes in a megabyte?
1000 kilobytes = 1 megabyte
How many megabytes in a gigabyte?
1000 megabytes = 1 gigabyte
What is a character set?
a defined list of characters recognised by both hardware and software
What are two examples of character sets?
ASCII and Unicode
What is an advantage of Unicode over ASCII?
Unicode has a wider range of characters
What is an advantage of ASCII over Unicode?
ASCII is 7 bit code so it takes up less storage space
What is a pixel?
A basic unit of programmable colour
What is a bitmap image?
Pixels joined together to form a bitmap image
What is colour depth?
Colour depth is the number of bits per pixel
Why does sound need to be converted into a digital form to be stored on a computer?
Because analogue sound has an infinite curve on its wavelength so it needs to be converted into a finite curve in order to be stored
What is sampling rate?
The number of samples per second of a digital sound
What is the sample resolution?
the number of bits used per sample
What is the equation for sound file size?
sample rate x sample resolution x number of seconds
What is the equation for bitmap image size?
image width x image height x colour depth
What is data compression?
Data compression is a way of making data smaller / more compressed
What is lossy compression?
When data is compressed by removing some of the data, eg removing pixels from an image
What is lossless compression?
When data is compressed but none of the data is removed.
What is run length encoding?
A simple form of lossless compression where runs of data are stored in frequencies,
How can data be compressed by huffman coding?
It reduces the number of bits per character the more frequently the character is used.
