Flashcards
Storage
Cards in this deck (23)
- 1VolatileRequires constant power supply to retain data
- 2Non-volatileRetains data regardless of power supply - does not require power to retain data
Also known as persistent memory - 3Primary storageRAM, ROM and CPU cache
Directly accessible to the processor
Located on the motherboard/processor itself
Often volatile storage - 4Secondary storagePersistent (non-volatile)
CPU cannot access it directly
Examples include magnetic storage, SSDs and optical disks
Physically exists - 5Tertiary storagePersistent
Abstract storage - does not physically exist on the computer
Examples include cloud storage and centralised NAS/SAN devices on LANs - 6Magnetic StorageUses very small magnetised areas in multiple tracks (either parallel on tape or in concentric circles on a disk)
Areas are magnetised in different directions to represent bits (0 or 1)
Areas are read by a read/write head, which is stored out of the way when not in use - 7Advantages of Magnetic StorageLow cost per bit when compared to other forms of storage
Reasonably fast to access data
Can have a very large capacity (1-2TB for stacked hard disks) - 8Disadvantages of magnetic storageSlower than other forms of media
Moving parts are susceptible to wear and tear
Generate a lot of noise and heat, so may need a cooling system - 9Examples of magnetic storageMagnetic tape
Floppy disks
Hard disks - 10Optical storageData is stored in a spiral track on a reflective disk
A laser is used to create pits (dents) and lands (flat sections) on the disk to represent 0s and 1s
The same laser at a lower power may also be used to read the disk
Storage capacity depends on the width of the track and the wavelength of the laser used to read/write data - 11Types of optical storageRead-only: Laser is used to remove sections of reflective material to write everything to zero - changes are permanent
Read-write (rewriteable): A laser and magnet may be used to heat an area of the track then reshape it (CD-RW), or an alloy with different states may be used (DVD-RW) - 12Advantages of optical storageCheap to produce
Easy to distribute - 13Disadvantages of optical storageEasily damaged - scratches or excessive sunlight can make parts of files unreadable
Very small storage spaces (up to around 50GB)
Slow to access data - 14Solid-state storageUses semiconductor cells to store individual bits
Housing and software used to make it behave like a hard drive
Persistent cells are commonly NAND flash memory
Generally used for portable devices e.g. phones, media players and 2-in-1 laptops - 15Advantages of solid-state storageMuch faster than other forms of memory
No moving parts, so not susceptible to wear and tear
Less susceptible to accidental damage
Produce no noise and very little heat - 16Disadvantages of solid-state storageHas the highest cost per bit of the three types of storage
Difficult to manufacture
There may be a read-write limit if other forms of storage are used (e.g. EEPROMs) - 17Hybrid storage systemsSome computers may combine the benefits of both magnetic storage and SSDs by utilising both
In these cases, the data most directly associated with improved performance is stored on the SSD to be accessed faster, while everything else is stored on the magnetic drive. - 18Erasing dataIn most cases, a file is not erased from storage when it is deleted - only the pointers to that file are removed
This marks the file's location as empty without removing the file itself.
When new files are saved, the location of the old file is rewritten where necessary and new pointers are created - 19RAMRandom Access Memory
Volatile memory used to store programs and data currently in use on the computer. - 20ROMRead-Only Memory
Non-volatile memory present on the motherboard
Used to store programs that must remain in memory, such as the bootloader and BIOS - 21Virtual Memory (Emulated Memory)RAM has a finite capacity, but the combined size of running processes may exceed this
In order to cope, a sector on secondary storage may be used as an extension of RAM (often called virtual or emulated memory)
Running processes are kept in RAM whereas idle processes are kept in virtual memory - 22Advantages of virtual memoryExtends RAM capacity, allowing processes to continue after it has been filled
Allows very large files to be loaded into RAM and accessed as needed
Improves main memory efficiency - 23Disadvantages of virtual memorySecondary storage is engaged more often, which may decrease its lifespan
More limited space on the drive as a section has to be reserved for a page file
If RAM is constantly filled then the OS spends most of its time swapping pages, which keeps the secondary storage engaged and reduces performance (this is known as disk thrashing)
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- A level OCR A level Computer Science (Topic 1 - Components of a Computer) Flashcards on Storage, created by James Norman on 23/11/2018.
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- James Norman
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