Unit 1.3 - {Storage} v2

Unit 1.3 - {Storage} v2

1. Types Of Storage

   • Optical
     • Definition: Device that uses a laser to read and write
     • Devices: Blu Ray DVD CD ROM
     • Characteristics: Cost is mid-range out of all three types of storage and is also mid-range when it comes to durability and portability
     • Has a large capacity
   • Magnetic
     • Definition: Read/write, move across the medium and change how magnetised that part of the medium is
     • Devices: Hard Disk Drive and Tape Drive
     • Characteristics: Has the best capacity, best cost and mid-range speed and portability
   • Solid-State
     • Definition: Made up of micro-chips (switches)
     • Devices: Solid State Drive, SD Card, USB Memory Stick
     • Characteristics: Has the best speed, portability, durability and reliability out of all three different types of storage
   • Storage Ranking

2. Six Characteristics Of Storage

   • Capacity: How much data it can store
   • Speed: How fast it accesses the data
   • Portability: How easy it is to move it from one place to another
   • Durability: How durable it is if dropped
   • Reliability: How well it consistently performs
   • Cost: How expensive it is per KB, MB and GB

3. What is Secondary Storage? Secondary storage is long term storage of data, files, software and OS

   • Why do we need to store them? To access it again later, to use software, to interact with the computer
   • What would happen without it? Software would need to be installed every time that you used it and you couldn't save any files, data, images or videos etc

4. Computers use primary memory such as random access memory (RAM) and cache to hold data that is being processed. However, this type of memory is volatile, which means it loses its contents when the computer is switched off. General purpose computers, such as personal computers and tablets, need to be able to store programs and data for later use.

   • Computers use primary memory such as random access memory (RAM) and cache to hold data that is being processed. However, this type of memory is volatile, which means it loses its contents when the computer is switched off. General purpose computers, such as personal computers and tablets, need to be able to store programs and data for later use.
     • magnetic storage devices, such as hard disk drives optical storage devices, such as CD, DVD and Blu-ray discs solid state storage devices, such as solid state drives and USB memory sticks
       • As the disk is spinning, a read/write head moves across its surface. To write data, the head magnetises or demagnetises a section of the disk that is spinning under it. To read data, the head makes a note of whether the section is magnetised or not. Magnetic devices are fairly cheap, high in capacity and durable. However, they are susceptible to damage if dropped. They are also vulnerable to magnetic fields. A strong magnet might possibly erase the data the device holds.
         • Optical devices Optical devices use a laser to scan the surface of a spinning disc made from metal and plastic. The disc surface is divided into tracks, with each track containing many flat areas and hollows. The flat areas are known as lands and the hollows as pits. When the laser shines on the disc surface, lands reflect the light back, whereas pits scatter the laser beam. A sensor looks for the reflected light. Reflected light (lands) represents a binary '1', and no reflection (pits) represents a binary '0'.
   • There are many forms of secondary storage and each type of secondary storage device has its own characteristics. Because all devices are different, some are more suited to certain applications than others.
     • Not all computers require secondary storage.Embedded computers, such as those found in a digital watch or central heating system, do not need to store data when the power is turned off. The instructions needed to run them are stored in ROM and any user data is held in RAM.
   • For example, a hard disk drive has a high capacity and reasonable access speed, making it suitable for everyday storage of programs and data. A USB stick is smaller in capacity, but extremely fast and portable, making it suitable for transferring files between computers.

Images and files in the map