IGCSE Theory Section 3-Storage devices and media

Section 3: Storage devices and media
Candidates should be able to:
(a)  describe common backing storage media (including magnetic tapes, hard discs, all forms of CD and
DVD, memory sticks, flash memory) and their associated devices
(b)  identify typical uses of the storage media, including types of access (e.g. serial/sequential, direct/
random) and access speeds

• Fixed hard discs Used to store operating systems, software and working data.  Any application which requires very fast access to data for both reading and writing to.  Not for applications which need portability.  Used for online and real time processes requiring direct access.  Used in file servers for computer networks
• Portable hard discs Used to store very large files which need transporting from one computer to another and price is not an issue.  More expensive than other forms of removable media
• Magnetic tapes Any application which requires extremely large storage capacity and speed of access is not an issue.  Uses serial access for reading and writing.  Used for backups of file servers for computer networks.  Used in a variety of batch processing applications such as reading of bank cheques, payroll processing and general stock control
• Optical backing storage media such as CDs and DVDs CDs tend to be used for large files (but smaller than 1Gb) which are too big for a floppy disc to hold such as music and general animation.  DVDs are used to hold very large files (several Gb) such as films.  Both CDs and DVDs are portable i.e. they can be transported from one computer to another.  Both can be used to store computer data
• CD ROM/DVD ROM Applications which require the prevention of deletion of data, accidental or otherwise.  CDs used by software companies for distributing software programs and data; by music companies for distributing music albums and by book publishers for distributing encyclopaedias, reference books etc.  DVDs used by film distributors
• CD R/DVD R Applications which require a single eburningf of data, e.g. CDs Z recording of music downloads from the internet, recording of music from MP3 format, recording of data for archiving or backup purposes.  
• DVDs Z recording of films and television programs
• CD RW/DVD RW Applications which require the updating of information and ability to record over old data.  Not suitable for music recording but is very useful for keeping generations of files.  DVDs have between five and ten times the capacity of CDs
• DVD RAM Same properties as DVD RW but quicker access and data can be overwritten more easily.  Similar to floppies in nature but has 3000Z6000 times more storage and uses optical technology
• Blu-ray Capacities of 25Gb, 50Gb and 100 Gb.  Used for storing films (movies). 25Gb equates to 2 hrs HDTV, 13hrs standard definition TV.  It is possible to playback video on a disc while simultaneously recording HD video.  (Will be) used for storage of PC data
• Solid state backing storage Smallest form of memory, used as removable storage.  More robust than other forms of storage.  More expensive than other forms, but can be easily written to and updated
• Memory sticks/Pen drives Can store up to many Gb.  Used to transport files and backup data from computer to computer
• Flash memory cards Used in digital cameras, palmtops, mobile phones, MP3 players