Storage Media

Data needs to be stored for later use on storage media. If the volume of data that needs to be stored is small, floppy disks are enough. However, when the amount of data to be stored is huge, storage media with larger storage capacities are required. In this section, you will learn about three such storage media - Cartridge Tape, CD-ROM and Magneto-optical disks.

Cartridge Tape

Assume that an organization has bought a powerful computer to meet its growing needs. The problem now is to shift the massive databases (e.g. a collection of related files, in which an employee database can contain employee code file, attendance file, loan file, leave file, etc.) from the old machines to the new ones. Using diskettes as the backup medium is cumbersome, as they cannot store large amounts of data. In such cases, a cartridge tape is a very convenient backup media as it can store many megabytes of data. Cartridge tapes are available in capacities of 60 MB, 150 MB and 500 MB.

Cartridge Tape

A cartridge tape is made of plastic, coated with a magnetic material, and is similar to a video cassette tape. The tape is divided into tracks, which run along the entire length of the tape. Data is recorded along these tracks. Just as you need a disk drive to read or write data onto a disk, you need a cartridge tape drive which is an input-output device for a cartridge tape.

Data on a cartridge tape is stored sequentially. Therefore, if you want to access data stored at the end of the tape, you will have to run through the entire tape till you come to the end. This is in direct contrast to accessing data on disks wherein data can be accessed randomly. A good analogy here is the audio tape or the gramophone record. If you want to listen to a song recorded in the middle of the tape, you have to forward the tape till you come to the point where the song starts whereas in the gramophone record you can directly place the gramophone head on the required sound track. Cartridge tapes are used wherever the volume of data or software to be backed up is very large, for example, backup copies of DBMS. Cartridge tape drives are present only in large machines.

CD-ROM

Imagine that you are viewing a video film about an Antarctic expedition on your computer. It would be ideal if you can see the recording of the expedition, hear a commentary on the expedition at the same time and listen to the conversation of members of the expedition on your computer. All this and more is possible using a CD-ROM (Compact Disk Read Only Memory) as a storage medium. The CDs used in a CD-ROM are similar to audio CDs and can store vast quantities of data—600 MB or more

To read a CD-ROM, you need an input device called the CD-ROM drive. A CD-ROM can not be erased or written onto without the help of a special device called the CD-Recorder.

CD-ROM and CD-ROM Drive

CD-ROMs are used whenever large volumes of data need to be stored and distributed. Databases on medicine, tourism, literature, etc. are available on CD-ROMs. Encyclopedia and dictionaries are also available on CD-ROMs.

Magneto-optical Disk

The data storage requirements of organizations have increased manifold. Software has also become powerful and, at the same time, voluminous. With usually more than several hundred megabytes or even gigabytes, the storage capacity of 1.44 MB diskette is insufficient.

Maxell Corporation, USA, has developed a 314 inch Magneto-optical (M-O) disk, having storage capacities in excess of 640 MB. M-0 disks with capacities of 2 GB are also available. Data can be read as well as written onto these disks. The new disks are compatible with all 3W inch magneto-optical drives, such as those manufactured by Fujitsu, Olympus, and others. Some of the significant improvements of the M-0 disk over the conventional 1.44-MB diskette are:

• Write speed that is more than 100% faster than the speed of conventional media. This is achieved by bypassing the erase data phase during a rewrite operation. Thus data can be directly overwritten on existing data during an overwrite operation.
• If the M-O disk is double-sided, it can store up to 4GB of data, which is more than what many hard disks can store.
• An archival life of more than 30 years, the disks are rewriteable over 1 million times.
• Protective layer of exceptionally durable hard coating to safeguard surface from heat or moisture.

Some applications of the new M-0 media include: mass archival storage, document/image storage, and multimedia storage using data compression technology.

Magneto-optical Disk

Now that you have become familiar with the PC environment, you will see where the PC fits in the computer spectrum. You will be given a bird's eye view of the computer range, from micro-computer (of which the PC is a well-known example) to supercomputers, the emphasis being on their capabilities and application areas. In this session, you will also take a closer look at the PC range itself.