Common storage technologies

2.1.2 Computer hardware

a) Purpose of the CPU

b) Function of the CPU

c) CPU characteristics

d) Binary

e) Logic diagrams

f) Truth tables

g) RAM v ROM

h) ROM

i) RAM

j) RAM and performance

k) Virtual memory

l) Cache

m) Flash memory

n) Memory technologies

o) The need for I/O devices

p) Input devices

q) Output devices

r) I/O and specific needs

s) Secondary storage

t) Common technologies

u) Suitable storage devices

2.1.2 t) Common storage technologies

Introduction
There are three main tpyes of technology for storage. These are solid state, magnetic and optical.

Storage

Solid state devices
Solid state devices have no moving parts. That means they can't get worn out and are not quite as easily damaged by bangs and knocks as optical and magnetic devices. They store store data in binary patterns using billions of tiny switches. Another point to note about solid state devices is that they need very little power to work and can get the power that they do need from the device that they are plugged into. Examples include, SD cards, micro SD cards and pen drives.

Magnetic devices
These store binary data patterns as billions of magnetised areas on a disk. These areas can be read from or written to by a special head that moves over the magnetic area. With hard disk drives and floppy disk drives, the disk spins very quickly (thousands of times a second) whilst the head moves over the magnestised areas, reading from and writing data to the disk. One of the things to look out for if you ever have to buy a new hard drive is how fast the disk or disks spin (hard disks often have more than one disk inside them) - the faster they spin, the quick reading and writing data can take place so the faster your computer can work.

Optical devices
Optical devices store binary patterns using lasers. The lasers shine onto a disk and change whether an area on it can reflect light or not. The laser can then be used to read back patterns by shining a laser on the disk and looking at which areas reflect light and which don't. Some types of disk can be written to just once, although you can read from them many times. These are known as 'WORM' storage devices (Write Once Read Many). CD-ROMs, DVDs and Blu-ray disks are examples of WORM disks. They are often used by manufacturers to distribute software. Other media, such as CD R/W can be written to many times as well as read many times.

Q1. Explain with examples what is meant by a ‘solid state device’.
Q2. Suggest one way of improving a computer’s performance, related to the hard drive.
Q3. What is meant by a storage medium described as a WORM storage medium?
Q4. Give an example of a WORM medium.
Q5. Explain how a CD writer stores data on a CD.