Data or information stored on your computer may be stored on fixed disk drives within the computer or on removable media, such as CDs, that can be inserted and removed. Removable media can be used to transfer files between computers or to back up data that already exists on fixed drives. There are three types of removable media: Magnetic, Optical, and Flash.

magnetic storage
Magnetic storage: Hard drives, floppy disks, and digital audio tapes are examples of magnetic storage. They operate via a read/write head, which creates and reads magnetic impressions on the disk.

The low…

  • Magnetic printing only lasts for about five years.
  • The capacity of most removable magnetic disks is too low for many types of files.

optical storage

Optical storage contains information in digital form that is written and read by a laser. All CD and DVD devices are examples of this.

The positive…

  • Higher capacity: an optical disc can store the same amount of data as more than 500 floppy disks
  • Durability: last up to seven times longer than magnetic forms of storage

Flash memory (solid-state removable storage)

Solid-state memory (or Flash memory) is a high-performance, plug-and-play storage device that contains no moving parts. It is found in digital cameras, game consoles, and digital audio players. You can use it in the form of USB flash drives to transfer or backup data. Flash memory is small, light, and fast.

Backup is the copying of files onto portable media so that if your computer fails, the data is not lost to oblivion. Backup is usually routine in large companies, but is often neglected by individual users. Some suggest backing up data files and mirroring your hard drive on a weekly basis. It takes about 45 minutes to back up a 500 megabyte hard drive.

There are two options: local or Internet backup. The following is a list of local backup options. Most of these also function as devices used to transfer data between computers.

  • Floppy
  • zip drives
  • CD
  • DVD
  • flash drive

Internet Backup
Another backup option is to send your files to an Internet site for safekeeping. If your computer crashes, you can simply download them from the site. Here are some examples of such sites: Backup Defender ( and My Backup ( NB The author does not recommend or endorse any of the above service providers.

Floppy disk
A floppy disk is a 3.5-inch removable magnetic disk. The earlier version, the floppy disk, is 5.25-inch square and flexible. Copying to a floppy disk is fast and inexpensive.

Ideal for…

  • Those who use their PC for personal finance: the floppy disk allows you to retrieve checkbook balances, etc.
  • Projects that need continuous support such as a movie script, since it is an economical alternative.

Not so good for…

  • Some newer models of computers and laptops that do not have a floppy disk or floppy drive installed.
  • Large amounts of data as floppy disks do not have a large storage capacity

zip drives
A Zip drive is a small, square-shaped magnetic disk that is ideal for backing up your PC. The 100 megabyte size contains the equivalent of 70 floppy disks. They also come in a size of 250 megabytes.

Ideal for…

  • Duplicate your entire drive
  • file
  • Store graphic images or other large files
  • large file transfer
  • Keep certain data separate from the files on your hard drive

The low…

  • They seem to be short-lived technology: most computers don’t have a Zip Disc drive installed, and opinion varies on how long they’ll be around.


There are different CD standards that have different capacities. Just to confuse us, they are recognized by apparently similar acronyms; CD-R, CD-RW, CD+RW, DDCD and E-CD.

CD-R (Compact Disc – Recordable) is a CD that can be recorded only once. It typically contains 74 minutes of audio or 650MB of data, although newer versions contain up to 80 minutes of audio (700MB of data). If your PC has CD burning software and a compatible CD-R or CD-RW drive, the CD-R can be used in the same way as a floppy disk. Unlike a floppy disk, however, it cannot be erased or overwritten. Look for CD-Rs that have an added protective layer that makes them less susceptible to scratch damage.

Ideal for…

  • make music cd
  • store photos
  • permanent data storage

Not so good for…

  • Transfer files as they can only be used once


A CD-RW (rewritable compact disc) and a CD+RW can be recorded as many times as desired. Data can be overwritten and deleted. Other than this, the CD-RW is identical to the CD-R. If it weren’t for their finite durability, CD-RWs and CD+RWs could be reused infinitely.

Ideal for…

  • file transfer
  • Temporary data retention

Not so good for…

  • Maintain important permanent files, in case they are accidentally deleted

Double Density CD (DDCD)

This disc has a much larger storage capacity than an average CD-R or CD-RW.

Ideal for…

  • Back
  • Archival data storage

enhanced CD
Enhanced CD (E-CD) is an audio CD with CD-ROM data added to it. The CD-ROM data is added in the space not occupied by the audio. Recording artists can use this to include videos, lyrics, interviews, or promotional material. The E-CD can be played in a CD player, but to view additional material you need access to a multimedia-capable device such as a CD-i player, DVD-ROM or CD-ROM drive.

bridge discs
A CD-Bridge disc contains additional information on a CD-ROM XA track. The disc can be played on a CD-i player connected to a television or on an XA CD-ROM drive connected to a computer. Software like Photo or a karaoke CD player can provide a lot of fun with Bridge Disk.

DVD (digital versatile disc)
Although DVDs have become more associated with video, they can also contain audio and computer data; hence its name Digital Versatile Disk. Like the CD, a DVD is a disc that is 120mm by 1.2mm thick. However, the DVD has more tracks than a CD, so it contains much more data. CDs have a constant storage capacity of 750 MB, while DVDs hold up to 17 GB.

A variety of acronyms are also used to distinguish between the different types and capacities of DVDs available. These include DVD-ROM, DVD-R, DVD-RW, DVD+RW, and DVD-Audio.

DVD-ROM (Digital Versatile Disc – Read Only Memory) is similar to a DVD movie, but it is designed for computers. The DVD-ROM stores data in the same way that the CD-ROM does and is used in the DVD-ROM drive of your PC.

The positive…

  • Larger storage space: stores more data than a CD
  • It can be filled with almost anything; video, music, or computer-specific data
  • At a base speed of 1.32 megabytes/sec.

The low…

  • Many older computers do not have a DVD-Rom drive installed.
  • Can only record once

DVD audio

DVD-Audio (DVD-A) is designed for high-quality music and audio data. Its storage capacity is seven times greater than that of a CD and provides at least twice the sound quality. Like the Enhanced CD, DVD-A can contain other data, providing the listener with additional information, such as lyrics or images. Many predict that DVD-A will replace the standard audio CD in the music industry.

Like the CD-R, the DVD-R (Digital Versatile Disc Recordable) can be recorded once.

The positive…

  • A DVD-R can contain a variety of information; video, text, audio and computer data
  • A DVD-R can be played in your regular DVD video player, but remember that if you have additional data that doesn’t have the same format, for example video and audio together, you’ll need a DVD-ROM or media player of some kind.
  • A DVD-R is read at the same speed as commercial DVDs.


Similar to CD-RW, a DVD-RW or DVD+RW (Rewritable Digital Versatile Disc) can be recorded, rewritten, and erased multiple times. Other than this, they are identical to DVD-R. DVD minus and plus are just different versions with the same functionality.

The future of CD/DVD storage
Most of the technology industry predicts that DVDs, with their higher storage capacity and faster access time, will soon replace CDs. DVD-ROM drives are likely to be sold with new computer systems in the same way that CD-ROM drives were once sold. However, we are always on the cusp of new technologies, such as HD-ROM.

HD-ROM (High Density Read Only Memory)
HD-ROM uses a more precise particle beam to write data. This allows the information to be written onto more durable materials, such as metal, making storage virtually permanent. HD-ROM has hundreds of times the storage capacity of CD-ROM.

flash drives
A flash drive is a small portable memory card that contains between 1 Mb and 1 GB of data. It’s surprisingly lightweight and is often worn around the neck or carried as a modern key ring. They are compatible with any PC with a USB port and with Mac OS 9 and OS X, Windows 2000 and XP, or Linux 2.4.17.

The positive…

  • Durable: longer than CDs or DVDs
  • No need for batteries or a separate power source
  • Convenient: Your computer should recognize the additional drive as soon as you insert it into the USB port
  • Ideal for backup
  • Higher storage capacity than many other portable devices
  • More portable than ZIP, CD, and floppy drives
  • Fast transfer rate (approx. 1 Mb/sec)
  • Edit, rewrite, delete as many times as you like
  • Help desk staff can use flash drives as a portable toolkit that includes system updates and recovery tools.

The low…

  • More expensive than other portable devices
  • Viruses: The portability and compatibility of the flash drive increases the chance of spreading viruses. In many cases, viruses carried by a flash drive will not be detected, since most antivirus programs are reactive and only recognize known viruses.
  • Theft: A flash drive can make it easy to steal data from an unlocked PC
  • Poor security: The size and weight of the flash drive make it very easy to misplace. Most have few or no security features and data is easily accessed. Some flash drives have built-in security; either a password or, in some cases, a fingerprint system, but this comes at a price.