memory Flashcards
primary storage
volitaile with the exception of rom
computers beed primarily storage because access times are faster
primarily storage holds data and instructions
primary storage is used as short term working memory
secondary storage
non volatile
large capacity
what is ram
ram is primary storage that holds data and instructions that are currently in use
ram is volatile
ram is very fast
ram is read/write which means data can be read from and written to
what is rom
rom is primary storage that holds the first instructions a computer needs to start up
rom contains the bios
rom is fast memory but slower than ram
rom is non volatile
rom is read only
what is virtual memory
virtual memory is an extension of primary storage located on secondary storage
when ram is nearly full virtual memory is used
programs and data not currently being excuted are transferred to virtual memory
slower than ram
why do you need secondary storage
long term storage of programs and data not currently in use
slower than primary storage but capacity is much higher
common types of storage
magnetic
solid state
optical
what is magnetic storage
magnetic storage is a type of non volatile media that uses magnets to store binary 0s and 1s
advantages and disadvantages of magnetic storage
advantages
high capacity
low cost per gb
decent speed
disadvantages
not very durable
inconvenient to be portable
not very reliable
and noisy
what is solid state storage
solid state storage is a type of non volatile media that used electronic circuits to store binary 0s and 1s
advantages and disadvantages of solid state storage
advantages
high storage
very fast
durable
portable
disadvantages
high cost
not reliable
optical storage what is it
optical storage is a type of non volatile media that uses lasers to burn the surface of a disk creating pits and lands suitable for storing binary 0s and 1s
advantages and disadvantages of optical storage
advantages
low cost
durable
protable
disadvantages
low capacity
slow
not reliable
from smallest to largest the units of storage
bit, nibble, byte, kilobyte, megabyte, gigabyte, terabyte, petabyte
4 bits make a nibble
8 bits makes a byte
1000 bytes is a kilo byte
1000 kilo bytes is a megabyte
1000 megabytes is a giga byte
1000 gigabytes is a terabyte
1000 terabytes is a petabyte
hexadecimal values
A=10
B=11
C=12
D=13
E=14
F=15
what is an overflow error
an overflow error is occurs when a binary value is larger than the bits available
name two character sets
ASCII unicode
what does the quality of the image depend on
the total amount of pixels
equation for file size
file size= resolution x colour depth
colour depth meaning (bit depth)
the number of bits that are used to represent each pixels colour
what is meta data
additional data about a file
what happens if you change colour depth
image size decreases and quality decreases
what happens if you lower the resolution
lowering the resolution can lead to a quality decrease and an image size decrease.
analogue sound waves must be what
analogue sound waves must be digitally recorded and stored in binary to record the sound the amplitude (height)of the analogue sound must be measured and recorded in binary at specific intervals.
how to get the highest quality sound for sound waves.
to get the highest quality sound many samples are taken to recreate the analogue wave as closely as possible
what is sample rate?
sample rate is the number of times per second the amplitude of the sound wave is measured.
higher the sample rate better the quality but higher the file size because there is more data to store
what is bit depth?
the number of bits used to represent each sample.
higher the bit depth better the quality but higher the file size.
how to calculate file size
file size=sample rate x bit depth x duration
what are the types of compression
lossy compression
lossless compression
what is compression and what are the benefits?
to compress a file means to make it smaller
benefits include
files take up less storage
files can be read and written to quicker
files can be transferred quicker
what is lossy compression?
lossy compression is the removal of data from a file that can be seen/heard sometimes depending on what was removed.and it is permanent.
what are the advantages and disadvantages of lossy compression
advantages
file is smaller
file is transferred quicker via internet
can be used for images audio or files.
disadvantages
data is permanently deleted so you cannot go back to the original form of the file.
may also be noticeable that the data has been removed so quality may be worse.
what is lossless compression?
lossless compression reduces the file size without removing any data. because of this the file can turn to its original form since no data is lost so no quality is lost.
advantages and disadvantages of lossless compression.
advantages
data is not lost
file can return to original form
file size decreases
disadvantages
usually only used with files that would not work if data was removed e.g programs, games , word documents and executable files
