Title: Know the main types of storage media
Course: Module 1, Concepts of Information and Communication Technology (ICT)

Hard disks

Hard disks consist of a number of rigid magnetic disks in a protective casing. Data is recorded magnetically onto concentric circular tracks, each one divided into a number of sectors.
- Hard disks can hold very large amounts of data (equivalent to thousands or even millions of floppy disks) and are usually very fast in comparison to other storage devices. They vary considerably in terms of price, depending on their speed and capacity.

- Most hard disks are fixed inside the computer. Removable hard disks are available which can be inserted into and removed from a special bay without opening the computer case. However, these tend to be much more expensive.

- Because they offer the best performance and capacity in comparison to cost, fixed hard disks are the most common storage devices used in computers.

Floppy disks

Floppy disks are flexible magnetic disks held in a protective plastic jacket. They are sometimes known as diskettes. As with hard disks, data is recorded onto concentric circular tracks, divided into sectors.
- Floppy disks can only hold a small amount of data and are also relatively slow — accessing data on a floppy disk will take much longer than accessing data on a hard disk. However, floppy disks are very cheap, as is the drive needed to use them. They are also very portable because most computers have a floppy disk drive. Thus, floppy disks have remained popular despite their lack of speed and capacity.

- The standard size for a floppy disk is 3½". The floppy disks used with PCs usually have a capacity of 1.44MB. 120MB floppy disks are available, but they are more expensive and a special type of drive is required to use these disks.

Other magnetic disks

Other magnetic disk devices, such as Zip disks and Jaz disks, tend to cover the middle ground, in terms of both speed and capacity.

- The cost of a drive to use one of these disks usually falls in the same range as the cost of a standard hard disk. Faster drives that use higher capacity disks tend to cost the same as larger, faster hard disks, while slower drives that use lower capacity disks are similar in price to smaller, slower hard disks. Be aware though that because the drive has no storage capacity of its own, you also need to buy the appropriate disks to use.

- The disks tend to offer much less capacity than a hard disk — although much more than a floppy disk. However, each disk can cost anything up to the price of a small hard disk. The main advantage is that the disks can be removed and transferred elsewhere. Also, because you can have as many disks as you want, overall capacity is not limited, except by the cost of the disks and your budget.

Compact discs

A CD-ROM is a type of compact disk often used to supply data such as software. However, as we mentioned earlier, CD-ROMs are read-only and so cannot be used as storage devices for data copied from your computer.
- Another type of compact disc is a CD-R. This can be written to once only — after that, the data on the CD-R cannot be erased or overwritten. A special drive such as a CD-R or CD-RW drive is needed to write to a CD-R. However, the data on a CD-R can be read using a normal CD-ROM drive.

- A CD-RW is a type of compact disc that can be written to many times. However, a CD-RW can only be read from and written to using a CD-RW drive.

- The cost of a CD-R or CD-RW drive is typically the same as the cost of a mid-range hard disc, while CD-R and CD-RW discs are relatively inexpensive (much nearer the price of floppy disks than hard disks).

- CD-R and CD-RW discs can store up to 650MB of data, which is much less than most hard disks. The main advantage of CD-R discs over other removable storage devices (e.g. Zip disks and Jaz disks) is that most modern computers have a CD-ROM drive and so can read the data stored on a CD-R — although this does not necessarily apply to CD-RW discs.

- The main disadvantage of CD-R and CD-RW is they are quite slow in writing data — especially when compared to modern hard disks.

Important Points

- A DVD-ROM can hold far more data than a CD-ROM. This means a DVD-ROM can hold longer and better quality sound and video clips. One of the advantages of DVD-ROM over CD-ROM is that a single DVD can hold a complete feature film with better quality than you would get on a VHS videotape.

- The extra capacity of DVD-ROM makes it an ideal way to supply large multimedia files and applications.

Tape drives

Tape drives (or cartridge drives) can be used to store large amounts of data. Retrieving information from a tape drive is slower than from some other storage devices because the tape drive has to work its way through the tape to access the relevant information.
- Like floppy disks, Zip disks and CD-Rs, magnetic tape cartridges are removable and easy to transport. Many can store far more data than other removable storage devices, with some cartridges able to store more data than the largest hard disks.

- The price of tape drives varies far more than any other storage device. Some drives are about the same price as a mid-range hard drive, while others are many times the price. Tape cartridges tend to be relatively inexpensive.

Formatting a disk

Before you can work with a disk or tape drive you sometimes have to format it.

- Formatting is the process of preparing a disk or tape drive to hold data so that the operating system can read it or write to it.

- Typically, when you format a disk you will be able to set the file system (e.g. FAT or NTFS), the cluster size and the volume label.

- When you format a disk or tape, all the data on the disk is erased, so be careful!

- Most floppy diskettes are sold pre-formatted for PCs, so you may not need to format a floppy diskette before you use it. Also, you don’t need to format CD-R or CD-RW before you use it.

Storage devices

Which of the following are storage devices?

- DVD
Feedback: Correct!
- USB memory stick
Feedback: Correct!
- Hard drive
Feedback: Correct!
- Tape drive
Feedback: Correct!
- Random Access Memory (RAM)
Feedback: Incorrect, that is temporary memory only.