Hardware Storage Devices Flashcards
Secondary storage devices
Hard disk
Optical disk
Solid state disk
DRUM memory
Read-write heads
Stored more data than punch cards
Few Kb
Core memory
- no moving parts
- quicker
- made by hand
Floppy disk
- portable
- small
- 8 inch = 80Kb
What are hard disks made of
- hard metallic material
- hermetically sealed
- several in a stack
- counted with thin magnetic film
- changes in the direction of magnetism representing 0s and 1s
How are hard disks organised
Into concentric tracks
Each track is split into sectors
Sectors can be individually addressed by the OS
Examples of optical disks
CD
DVD
Blu-Ray
How are optical disks read and written to
Laser technology
How are optical disks organised
One single spiral track
- starts in the middle
What are optical disks made of
Land and pits as 0s and 1s
Protective layer to prevent data corruption
Writeable disks are coated in a photosensitive dye
Why can you fit more data on Blu-Rays
Because blue light has slower wavelength
SSD facts
- non-volatile
- NAND memory
How are SSDs organised
Into blocks
Blocks managed by a controller
What are SSDs made of
Semiconductors
Floating gate transistors
Control gate transistors
Layer of oxide
Floating gate transistors (FGT)
Trap and store charge
