memory and storage - primary and secondary storage

features of primary storage (2)

small capacity and volatile (except ROM)

features of secondary storage (2)

large capacity and non-volatile

why does a computer need primary storage

access times are much shorter so the time taken for the fetch-decode-execute cycle is much faster

what does primary storage hold

data and instruction that the CPU needs to access while the computer is turned on

what is RAM

primary storage that holds data and instructions that are currently in use

what is ROM

primary storage that holds the instructions a computer needs to start up including BIOS

features of ROM (2)

non-volatile and read-only

what is BIOS

basic input output system

what is virtual memory

an extension of RAM located in secondary storage

how does virtual memory work

programmes and data that are not currently in use are moved to virtual memory and brought back to RAM when needed.

disadvantage of virtual memory

much slower than RAM and negatively impacts performance which can be avoided by increasing size of RAM

what does secondary storage hold

long-term storage of data and programmes that are not currently in use

6 characteristics of secondary storage

reliability durability portability cost capacity speed

3 types of secondary storage

optical, magnetic, solid state

what is magnetic storage

storage that uses magnetism to store binary 0s and 1s

what is optical storage

storage that uses lasers to burn pits and lands into a disc to store binary 0s and 1s

what is solid state storage

storage that uses electrical circuits to store binary 0s and 1s

rank the types of secondary storage best to worst based on capacity

magnetic, solid state, optical

rank the types of secondary storage best to worst based on cost

optical, magnetic, solid state

rank the types of secondary storage best to worst based on speed

solid state, magnetic, optical

rank the types of secondary storage best to worst based on noise

optical and solid state, magnetic

what 2 types of storage has issues with durability

magnetic - moving parts can be damaged if dropped
optical - prone to scratches

what type of storage has issues with portability

magnetic - its bulky, heavy and has moving parts

what is the reliability for each type of storage

magnetic - prone to mechanical failure

solid state - limited read/write cycles
optical - reliable if looked after well

3 types of optical storage discs ranked from lowest to highest capacity

CD, DVD, blu-ray

examples of solid state storage

usb memory stick

memory card

solid state drives

examples of magnetic storage

hard disk drives

magnetic tapes