1.6 Storage Devices

• Volatile • Read and Write • Stores os, programs, data currently being used

• Non-volatile • Read only • Stores boostrap

An extension of memory to RAM using secondary storage

RAM which is volatile

Non-volatile storage

• Concentric racks are created on a magnetic disk • They can spin at high speeds from 3.6k to 7.2k rpm • Data is read or written as sector moves under the head • Spinning platters are read by drive heads

• Use electrically programmable non-volatile flash memory

• Durable • Faster • Consumes less power • Portable • More portable • More expensive

• Can stores up to 128gb • Very cheap • Can be used for password protection • Useful for transferring data between computers

• Different laser wavelengths ‘burn’ smaller pits • The spiral track can be more tightly wound, creating a longer track

• Read • Recordable • Re-writable

• Often best suited to optical disks • Cheap to manufacture and distribute • Robust during carriage • Lightweight

• “Pressed” at the time of manufacture • Software distribution

• Can be written to once • Copying documents

• Can be written, read many times, erased and written again • Short/medium term backup • Transferring files from one pc to another

High-capacity discs which can stores feature-length films