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what is a bit
a binary digit that can take the value of 0 or 1
units of data
bit - 1 bit
nibble - 4 bits
byte - 8 bits
kilobyte - 1000 bytes
megabyte - 1000 kilobytes
gigabyte - 1000 megabytes
terabyte - 1000 gigabytes
petabyte - 1000 terabytes
what is data capacity
maximum amount of information that a storage device can hold
how do you convert binary to denary
write out binary headings
put in the binary digits
add up the numbers with a 1 under it
how to convert from denary to binary
write out binary headings
put a 1 in columns which the heading fits into the denary number
how do you add binary numbers
add the binary numbers, 1+1 carries the 1 to the next column
what is an overflow error
when the result of a binary addition exceeds the number of bits available
why is hexadecimal used
it’s shorter than binary meaning its easier to understand and write with fewer errors (for humans)
how to convert to hexadecimal
convert to binary (if its denary)
split the byte into 2 nibbles and convert back to denary
convert it to hexadecimal
how to convert hexadecimal to binary/denary
convert the hexadecimal digits to denary
convert the denary into binary nibbles
put the nibbles together
convert from binary to denary (if converting to denary)
what do binary shifts do
left - multiply by powers of 2
right - divide by powers of 2
disadvantage of binary shifts (2)
if bits are discarded there could be a loss of precision
overflow errors occur when the value is too big to be stored within the number of bits available
what is a character set
a defined list of characters that can be understood by a computer
what is ascii
represents basic characters needed for english using 7 bits, representing a max of 128 characters
what is extended ascii
a character set using 8 bits that can represent a max of 256 characters including maths symbols
what is unicode
a character set using 16 bits that can represent all major languages and symbols.
disadvantage of unicode
takes up more storage space
what is a bitmap image
an image made up of pixels
what is a pixel
the smallest possible element of an image
what is a vector image
an image made from maths equations and points that are infinitely scalable
what is resolution
the total amount of pixels that make up a bitmap image
how do you calculate resolution
multiply height and width of the image in pixels
what is colour depth
number of bits stored per pixel in an image
how many colours would a 4 bit image have
24 = 16 colours
what happens when you increase bit depth
file size increases as number of bits per pixel increases
what happens when you increase resolution
file size increases as number of pixels increase
what is metadata
data about data
what are five examples of metadata
author, location, time, resolution, colour depth
what does frequency and amplitude in a sound wave represent
frequency - pitch
amplitude - loudness
what is A2D
when a computer converts an analogue sound wave to a digitial one
what is a sample
a measure of the amplitude of a wave
how do computers record sound waves
an anologue sound wave is sampled
amplitude is measured at set intervals
each sample is stored as a binary value
what is sample rate
the number of samples taken a second measured in hertz
what happens as you increase sample rate
the digital sound wave sounds more closer to the original and the file size increases
what happens as you increase bit depth
file size increases as the number of bits stored per sample increases
what is compression
reducing the the size of a file so that it takes up less space on secondary storage
what is lossy compression
when data is lost in order to reduce the size on secondary storage
what are three features of lossy compression
irreversible, greatly reduces file size, loses quality
what is lossless compression
when data is encoded in order to reduce the size on secondary storage
what are three features of lossless compression
reversible, reduces file size a bit, quality is not lost
what is a disadvantage of lossless compression (not about how much it can compress)
since the file has to be decompressed before being opened, it could increase file handling time
