1.1.3 Storage Flashcards
RAM
Random Access Memory
- Any location can be opened
- Holds data and instructions for currently running location
- Volatile
- Readable/writeable
- Very fast access
Volatile
The contents of the memory are wiped when you turn it off
ROM
Read Only Memory
- Holds the BIOS (used to start a computer) so it can’t be overwritten
- You can only read from it
Primary vs Secondary Storage
Primary is directly accessible to the CPU (RAM, cache ROM)
Secondary is additional storage
Storage device
The physical hardware that transfers the data onto the storage media
3 types of secondary storage
magnetic, optical and solid state
Magnetic storage
Spinning platters with read/write heads which use magnetism, read a sector at a time
Use polarised and unpolarised states, polarised has aligned poles that lets data be read, unpolarised scatters it
Magnetic storage advantages and disadvantages
+ cheap, huge capacity, fast read/write speeds
- not very portable, wear away, need power to continuously run (stopping running means it takes time to speed up), prone to failure
Virtual Storage
Extra storage is the main memory is full
Cloud storage: Data is stored online to be accessed on multiple devices
Virtual storage advantages and disadvantages
+ cheap, can access anywhere, unlimited capacity, durability relies on providers
- Third party (security issues), needs bandwidth, data can be lost if the storage array fails
Solid state/Flash
Commonly uses electrically programmed non-volatile flash memory
Use microchips and silicon semiconductors
Solid state advantages and disadvantages
+ no moving parts - less likely to break, more portable, faster read/write speeds, use less power so longer battery life and it makes no noise
- More expensive, lower capacity
Optical Storage
Uses a laser and light to process information
Different laser wavelengths burn smaller pits and lands on the track so it can be more tightly wound and longer
Pits represent 0, flats 1
Certain sections reflect or scatter light
Optical storage advantages and disadvantages
+ cheap to manufacture and distribute, lightweight, robust during carriage
- Quite expensive per GB, poor durability and reliability
CD formats
CD-ROM for software distribution
CD-R for copying and storing online
CD-RW for transferring and backing up files
