input, output storage devices Flashcards
ram, rom, flash, optical, ssd, HDD virtual memory
input device
can be used to put data and information into a computer.
output device
can be used to send information from the computer.
Optical
Optical devices are read from and written to using lasers.
Binary information is represented by portions of the disc which either reflect or scatter the incident laser light written in spiral tracks on the disc’s surface.
example of optical storage
- CDs - low levels of storage
- DVDs - higher levels of storage than CDs
- blu -ray - 5x higher storage than DVDs, useful for high resolution films
advantage of optical storage
CDs
small, thin, and light which makes them very portable
disadvantage of optical storage
CDs
easily damaged by scratches, their limited storage capacity and relatively slow transfer speeds.
Magnetic
represent binary information using two magnetic states: polarised and unpolarised. If a portion of magnetic material is polarised, all magnetic poles align and can be read by a read/write head passing over the region. If an area is not polarised, magnetic poles are randomly scattered and produce a different reading on a read/write head. These two states can represent 1and 0, allowing any information to be represented in binary form.
example of magnetic storage
- Hard Disk Drives (HDD)
- Magnetic Tape
- Floppy Disks
advantage of HDD
high capacities of between 500GB and 5TB.
disadvantage of HDD
slow data transfer speeds
their tendency to become damaged by movement.
The combination of brittle platters and moving parts results in a delicate device.
how do HDD work
They work by rotating magnetic platters at high speeds under a read/write head on an actuating arm. The combination of the arm and rotating platter allows the read/write head to access any part of the platter. Most HDDs will have multiple platters stacked on top of each other to maximise storage capacity.
flash storage
Flash storage is fast and compact. The technology makes use of silicon semiconductors forming the logic gates NAND and NOR to store electrical charge in one of two states: high or low. These two states represent the binary values True and False, which can be used to represent information.
advantage of flash
non-volatile, meaning it stores its data even when power is lost
disadvantage of flash memory
more expenstive per gigabye than other methods of storage such as optical or magnetic
advantages of Solid State Drives
are extremely light and portable, while having no moving parts - this makes them much more resistant to damage from movement
