In this chapter students will learn about:

  • Back-up storage
  • Why it is necessary to back up data and files
  • The types of access used by the backing stores
  • The types of internal and external backing storage devices:
  • Magnetic
  • Optical
  • Solid state

1 Bit = Binary Digit
8 Bits = 1 Byte
1024 Bytes = 1 Kilobyte KB
1024 Kilobytes = 1 Megabyte MB
1024 Megabytes = 1 Gigabyte GB
1024 Gigabytes = 1 Terabyte TB
1024 Terabytes = 1 Petabyte PB
1024 Petabytes = 1 Exabyte EB
1024 Exabytes = 1 Zettabyte ZB
1024 Zettabytes = 1 Yottabyte YB

punch cards
a punch card was the oldest way known how to actually store information, exept for writing by hand. They were created by Basile Bouchon. He used perforated paper to store paterns, which were little holes in the paper. these patterns were used to make cloth.
punched tape
Punch tape was a more advanced way of making punch cards. it was the same as punch cards, although longer and as a roll of tape, or strips connected to eqach other. Alexander Bain created the punch tape. Each row on the tape represented one character, which was significantly more efficient than the punch cards.
The selectron tube
The selectron tube was created by the RCA in 1946, and it was the first type of technological storage device. it could store up to 4000 KB and the bigger ones measured up to 10 inches in length! However, the selectron tube was very short lived on the market as they were over-powered a couple of years later by another new device. They were quite big and very expensive.
Magnetic tape
magnetic tapes started being created in 1951, and were very large, they were created for data storage. they could transfer an incredible 7,200 characters per second. They were metal, and would stretch in slength up to 350m and were therfore very heavy and hard to mobolise (if needed).
Magnetic drum memory
Magnetic drum memory was infact made in the 1930s, although it wasn't used for computer storage till the mid 50s. An IBM computer consisted of a 14 inch long drum, with a capacity of around 10MB. Links:
Hard disk drive
IBM created the first hard disk drive, which was very very big. It had 50 24-inch discs with a total storage capacity of 5 million characters (just under 5 MB). After some time, IBM released the first ever giga-byte capacity hard disk. it was the size of the refrigerator, and costed more than $100 000!!!
Floppy disk
The floppy disk was a very long-lived accesory that was very efficient for every day use. the first floppy disks were made for read-only, however in the dawn of 1980, they were created for read and write. The first floppy disks were actually quite big, 8 inches in length! Although passing through the years, they gradually came to a stop at 3.5 inches.
Laser disk
Laser disks were very convinient, and were really just the plans for the CD-ROM and other optical storage solutions. they were quite big, with a 30cm diameter, and they could play up to one hour of audio or video! The basic technology of these clever discs was actually invented way back in the late 1950s!
compact cassette
the compact cassete was very popular in the 80s. they were a popular way of storage on personal computers, and were also used for listening to music.
CD re-writable was created in 1979, however it was not actually fully used, and released into the market until 1982. it was very succesful, prooving itself much better than the floppy disk, later on in the years. It was also known as the compact disk.
CD- read only memory was made in 1985, and was also very succesful. they were used in every country, and practically pushed away the floppy disks, as th enew CDs could hold 4GB!!
Flash drives
Flash drives were very conveanient for personal data storage, and transfering data to different computers. they are aslo called USB s or USB flash drives, and they can consist of up to 32GB and much more.
Blu-Ray disks / HD-DVD s
these special disks are very new, and were created in early 2006. they function by using organic dyes, and look very much like CDs and DVDs. they can hold a capacity from 20GB to 40GB and do the same job as a CD ROM / CD R
holograpic versatile disk (HVD)
these are very new disks created, for use in the future. What would you say about having a Holographic Versatile Disc that could store 160 times more data than a Blu-Ray disc. 3.9 TB of data on one disc – or approximately 4,600 to 11,900 hours of video using MPEG4 encoding!!!!


Portable hard disc
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
Magnetic tape
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 CD and DVD
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
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
Applications which require a single ‘burning’ of data, e.g. CDs – recording of music downloads from the internet, recording of music from MP3 format, recording of data for archiving or backup purposes. DVDs – recording of films and television programs
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
Solid state backing
Physically the 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
Same properties as DVD RW but quicker access and data can be overwritten more easily. Similar to floppies in nature but has 3000 – 6000 times more storage and uses optical technology
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
Memory stick/pen
Can store up to many Gb. Used to transport files and backup data from computer to computer
Flash memory card
Used in digital cameras, palmtops, mobile phones, MP3 players