This immense hardware power of computers and other digital devices such as laptops and palmtops is harnessed by an operating system. It ensures that the phenomenal capability of the processors is channelled toward executing real-world tasks according to the needs of the user. For this, the operating system requires specialised software programmes that are tailor-made to do different functions. Computers generate a lot of data in their day-to-day work. This data has to be stored somewhere. A variety of data storage devices have been invented in the last couple of decades that can be used with computers and other digital devices.

There are about a dozen different types of storage media available in the market to suit every need. These are of two types ? removable and non-removable. Among the latter, the most prominent are the hard drives that exist inside every computer. These are the primary data storage devices and have huge capacities, with the commonly available ones in the market today touching the 160 GB mark. Nothing can come close to hard drives in terms of data access and write speed, reliability and storage capacity and they currently monopolise the non-removable data storage market.

Then there are the removable storage devices, such as USB drives, flash memory cards, CDs, DVDs, portable hard disks, floppy disks and so on. Their storage capacity varies from 1.4 MB of a floppy drive to 240 GB of a portable hard disk. In recent years, due to improvements in technology, the storage capacity and reliability of portable storage media have increased exponentially.

The most popular and most widely used removable storage media is the optical disks. These are a wonder of modern science and engineering. They are an ideal solution to a typical computer user's data transport and archiving needs. Optical disks are nothing but small circular disks made up of very tough plastic.

They store all their data on one side of their surface (the data side) in a pattern of small microscopic pits. The pits are arranged in a single groove that starts from the centre and goes around in circles, radiating out toward the edges. This pattern of pits is read by a laser that bounces off the surface (hence the name ?optical disks,? because the data is read by light and not by a magnetic head).

The oldest and still mainstream optical disks are the compact discs. When they were launched in 1982, they revolutionised the portable data storage media market. It was just unbelievable how such a small disk could hold up to 700 MB of data. Contrast this with the most commonly available storage device then ? the floppy disk ? that could hold a puny 1.4 MB of data.

CDs were quickly accepted by individuals and industries. Their fast and wide popularity destroyed the floppy disk business and they have now almost gone out of use. The biggest gainer was the entertainment industry that soon made CDs the media of choice for launching movies and music albums, which earlier used to come loaded in magnetic-tape cartridges. All software today also comes loaded on CDs. The introduction of rewritable CDs redoubled their popularity as a flexible and high-capacity data storage tool. CDs are currently ruling the portable storage market.

Recently, another version of optical disks called Digital Versatile Disks (DVDs) has been launched. These are a huge improvement over the CDs in terms of data capacity. They can hold a whopping 4.7 GB of data. So, has the time come to bid goodbye to the good old and trusted CDs?

The introduction of DVDs is a real threat to the monopoly of CDs in the data storage market. However, CDs are quite cheap. They come at only 1/7th the cost of a DVD. On top of this, CD writers are quite inexpensive compared to DVD writers. DVDs still pale in comparison to CDs in terms of popularity and wide usage. However, as the use of DVDs spreads and they become as mainstream as CDs are today, the cost of DVDs as well as the drive is bound to come down drastically. This has already started happening.

It seems, for some time at least, CDs will coexist with DVDs. There is a huge amount of data files whose size does not exceed a few hundred MBs, such as anti-virus or data-recovery software. For these, many would still prefer to go for CDs because of their low cost, while the high-capacity data storage market will be totally monopolised by the DVDs.