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Memory and secondary storage (Considerations for use (Capacity- how much…
Memory and secondary storage
Random Access Memory (RAM)
Main memory
Programs loaded from hard disk to memory to be used
Faster than retrieving data from hard drive
Volatile- data and instructions are lost in the event of power cut etc.
Virtual Memory
Takes over once main memory is full
Generally stored on the primary storage device e.g. hard drive
Slower as a result of read speeds from hard drive compared to main memory
Allows users to continue working by swapping currently used data between VM and main memory
Read only Memory (ROM)
Non- volatile- data is permanently stored
Data cannot easily be changed once stored
Used to store BIOS
Initiates loading of the OS when a computer system is turned on
Allows user to have basic input and output
Considerations for use
Capacity- how much storage is required for the file types you intend to save
Speed- how quickly do you want to retrieve the data or write the data
Portability-do you want to move the data around easily
Durability- how strong does the device have to be. is it going to be subjected to shocks and falls or is it fairly static.
Reliability- how long will the device and it's media last. moving parts make devices less realiable
Cost- more storage and faster speeds mean more cost; do the advantages outweigh the cost?
Types of storage
Magentic
Magnetic disks read by a moving head going across a platter.
Susceptible to damage due to moving parts- durability, reliability and portability reduced.
Can be affected by strong magnetic fields therefore not suitable for all uses.
Can be internal or external
Large capacity for lower costs, relatively quick
Optical
uses laser to read/write data to disks
CD available as CD ROM, CD-R, CD-RW.
DVD- higher capacity 4.7 Gb (single layer)8.5Gb (dual layer)
Blu Ray - up to 50Gb
Very portable
Durability depends on storage- prone to scratches and dirt which stop the lasers reading properly
Solid State
no moving parts
sometimes known as flash memory
very light
faster access times compared to magnetic storage
low power consumption- good for laptops/phones
very thin therefore portable
run cooler- therefore more efficient
expensive for large capacity
Cloud
Data saved off-site in large data farms- these are large warehouses filled with file servers
Can access data anywhere in world
Share data with others instantaneously
Backup of data centralised- someone else's responsibility
dependent on having am internet connection
fears over vulnerability to hacking and theft of data.
CPU
Embedded Systems
Computer Systems for a given purpose
Everyday examples
Sat Nav
Heating management on a washing machine
Timers etc on Microwaves
Built in engine management systems in cars
Cheaper to produce than a multipurpose computer
Failure of one system doesn't impact on another
eeProm- has firmware that can be updated via manufacturer if improvements have been made- common on internet enabled devices to enhance security.