memory and storage Flashcards
what are the different types of storage
- primary storage
- secondary storage
- tertiary storage
what are the differences between primary and secondary storage
- primary storage is volatile with the exception of ROM while secondary storage is non-volatile
- primary storage has a small capacity compared to secondary storage while secondary storage has a much larger storage capacity
- primary is much faster to access from than secondary
what is the need for primary storage
primary storage hold the data and instructions which the CPU needs access to while the computer is running and the CPU can access data from primary storage much faster than secondary
what is ROM
- small piece of read only memory located on the motherboard
- contains very first instructions for the computer
- loads the BIOS or bootstrap
what is RAM
- temporary storage of instructions and data
- hold information being executed by the processor
- volatile
- faster than the hard disk
what happens when a computer runs out of RAM
instructions that are not being used are transferred to a space on the hard disk
- known as virtual memory
what happens when you turn your computer on
- first it gets its initial instructions from the bootstrap contained on the ROM
- once this is complete instructions from the hard drive can be loaded into main memory (RAM)
where are instructions and data stored when you shut down your computer
on the hard drive as it in non-volatile, has a lot of capacity and also read + write
why is secondary storage needed
- storage of programs and data when the power is turned off
- semi-permanent storage of data that can change
- backup of data files
- archive of data files
what are the 3 common types of storage devices
- magnetic
- optical
- solid state
what are optical storage devices used for
to store music and images (for example movies)
how do optical storage devices work
by shining a laser at the media and processing the reflection from the media
what are the different types of optical storage devices
- CD-R
- CD-RW
- DVD-R
- DVD-RW
- Blu-Ray
what are the advantages of optical storage devices
- cheap
- light weight
- portable
what are the disadvantages of optical storage devices
- slow access times
- prone to scratches
what are the advantages of magnetic storage devices
- cheap
- large capacity
what are the disadvantages of magnetic storage devices
- slow access time
- fragile
- has moving parts
- perform better when defragmented
what are solid state drives
a piece of flash memory which operates without noise and are beginning to replace hard disks
how do solids-state drives work
they work by a flow of electricity forcing electrons into floating gates between two oxide layers
what are the advantages of solid-state drives
- durable
- fast access time
- no moving parts
- low power
- no need to defragment
what are the disadvantages to solid-state drives
- quite expensive
- limited number of read/write cycles
what are the requirements when deciding on which device to use given an application
- capacity
- speed
- portability
- durability
- reliability
- cost
when is optical storage suitable
- suitable for read only data distribution
- suitable for small capacity situations
when is magnetic storage suitable
- suitable when very high data capacity is required
- suitable for fast access to data
- suitable for low cost situations
- suitable for cloud storage on server farms
when is solid state storage suitable
- suitable for low power, small embedded systems
- suitable for rugged applications
- suitable for small to medium data capacity requirements
- suitable for silent operations
- suitable for very fast access to data
- suitable for situations where the devices need to be small and lightweight
how can you calculated the size of a text file
bits per character x number of characters
how can you calculate the size of a sound file
sample rate x duration x bit depth
how do you calculated the size of an image file
colour depth x image height x image width
how many bits of storage does a character on the standard ASCII set take
7
what is a nibble
4 bits
what is a byte
8 bits
what is a kilobyte
1024 bytes
roughly 1000
why do we use binary
- easier to manufacture
- therefore cheaper
- more reliable
what is hexadecimal
a base-16 number system through numbers 0-15
eg. 16 would be 1-0
how are the numbers 10-15 represented in hexadecimal
by the letters A-F
what is MSB
most significant bit (128 in an 8-bit binary)
what is LSB
least significant bit (1 in binary)
what are the steps of converting between deanery and hexadecimal
- write in out in binary first
- split the binary into 4 bits on a side
- now you can add the binary integers and write it in hexadecimal
how would you convert 12 into a hexadecimal
12 =
00001100 =
0000 1100 =
0 + C = 0-C or just C
what are the rules of adding binary
0 + 0 = 0
0 + 1 = 1
1 + 1 = 10
1 + 1 + 1 = 11
what is a binary shift
when you move all the numbers either to the left or the right
what is a character set
a defined list of characters recognised by the computer hardware and software, with each character being represented by a single number
what does ASCII stand for
American Standard Code for Information Interchange
how many bits are there in the ASCII character set
7, therefore there are 128 different combinations
what is unicode
a character set that has millions of international and multilingual characters and symbols
how bits is the unicode character set
its a 24 bit character set
what are the two ways of storing images in binary
- bitmap
- vector
what is a bitmap
when an image is made up of different coloured squares with each square having a binary value
what is a vector
when the mathematics to draw the image are stored instead
what is metadata
additional data stored with the image to define the width, height, colour depth and colour palette
what is the sample rate
how often per second we are sampling the original analogue sound
what is bit depth
amount of detail we are capturing with each sample
how can we improve the quality of the sound
- greater bit depth
- greater number of samples per second
however this also increases the file size
why do we use compression
- files take up less space
- maximise the amount you can store on a device
- smaller files are quicker to download and transferred
what is lossy compression
when some data is removed and discarded to reduce the overall amount of data and size of the file
eg. reducing the colour depth
what is lossless compression
when the file size is reduced without the loss of data however this doesn’t usually achieve the same file size reduction as lossy compression
when should you use lossy compression
- images
- sound
- videos
when should you use lossless compression
- documents
- executable files
