Optical Disks are currently the reigning monarch of portable data storage devices and are very popular with computer users. First introduced about 20 years ago, the optical disk technology has matured over time and become extremely reliable. Their costs have crashed too, with each disk costing almost as much as a floppy diskette. Also, they have capacities as high as 4.6 GB which is more than sufficient for the data storage needs of most computer users. There is hardly any other storage device available in the market today that gives such a fantastic combination of price, reliability and capacity as optical disks.

Optical disks are of two types: compact disks (CDs) and digital video disks (DVDs). The former were the first ones to be introduced, with a capacity of about 700 MB. CDs are today the portable storage media of choice for most computer and laptop users. Some years later, DVDs arrived in the market. These have a capacity of 4.6 GB that is more than sufficient to hold a full-length Hollywood movie.

The optical disks are used in tandem with an optical drive that is attached to a computer CPU. Once a disk is inserted into the drive tray, it is spun at a high speed by the drive motor. A read / write head that can move back and forth reads the data that resides on the disk surface as a pattern of microscopic pits. This is done by the medium of a laser emitted by the head which can not only emit it but also read it once it bounces back from the disk surface.

USB (Universal Serial Bus) drives are the latest data-storage devices to hit the market. These do not need stand-alone drives like optical disks. Instead, you simply insert the drive into the USB port of a computer or laptop, and it is ready to be used. Data can be saved to or extracted from the drive by the simple expedient of ?drag and drop.? The USB drives, which are small enough to be dangled by the end of a key chain (hence also called ?key chain drives?) are made up of a tough protective plastic shell inside which exists a flash-memory chip. All data resides inside this chip. There are no moving parts or a motor.

The USB drive technology is maturing very quickly. Already, the latest USB drives have a capacity of 12 GB, which is about three times higher than a DVD. Those with a capacity of 1 GB to 8 GB are available quite cheaply. USB drives offer many benefits over other devices. They have no moving parts, so there is no friction or energy consumption. They are quite small and easily transportable. You can copy and recopy data on them thousands of times without any problem. As their capacities go up and prices crash, USB drives are emerging as the storage technology with a bright future. Already, Sony has launched a laptop in the market that has a 60 GB flash-memory drive instead of a hard disk.

These are identical to the fixed hard disks found screwed inside a computer CPU, but made portable. The manufacturers try to build them as light and reliable as they can, and that is the reason why the market for portable hard drives is growing at a healthy rate.

These disks are small and thin enough to fit inside a shirt pocket. They connect to a computer CPU through the USB port. Most of these come with an automatic data-backup software that takes automatic backups of files. The main benefits of portable hard disks are their random access and huge storage capacities of up to 500 GB.

Tape drives have been around for many decades now and are still going strong. A tape drive system uses the tried-and-trusted magnetic tape technology to store data. It has two main parts ? the drive and the cartridges. The latter are made of plastic and carry a long and thin ream of magnetic plastic tape inside. This is the actual data-recording surface.

The cartridge is inserted into the tape drive where the spools are spun by the drive motor, moving tape from one spool to another. The tape moves past a read / write head, making full physical contact. The head has an electro-magnet that accesses and modifies data on the tape. A tape drive gives sequential access to data. These are ideal for archival storage of data because they are very cost-effective.