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Storage Devices

Hard Drives
CD-ROM Drives

Floppy and Portable Drives

For data to be portable, allowing it to be moved between computers, a computer needs some form of external storage devise. This has normally been done with the use of the 'floppy' external drive. In the past these drives have also been used to load programs, such as word processing, database and games into the computer.

The problem with modern(especially multimedia)computer programs is that they are so large and need a large number of floppy drives to contain their programs. For example a program such as Microsoft Word needs about 30 Mb of data space. As the 3.5' floppy drive only has 1.44Mb of space on the disk, a large number would be required to contain the program. Using various compression techniques, about fifteen, or twenty, disks would be required. Normally, these large programs are now sold on CD-ROM disk, which can store up to 620 Mb of data.

The problem with CD-ROM, of course, is that data can only be read from them, although there are systems of read/write CD-ROM drives coming on to the market. At present, however these tend to be expensive but are coming down in price.

Floppy Drives

The old 5.25 360K floppy drive of the eighties would hardly be enough to store an average graphic or Windows Word file today. The 3.5 drive, now sold with most computers, is able to store 1.44 to 2Mb. This is also becoming inadequate when used with the modern system.

Although there are attempts increase its storage space, using various compression techniques, the future seems to be with other devices such as the removable ZIP or optical drive. Although I would not throw away my floppy drive just yet provision need be considered for other external storage devices. At present the 3.5' floppy drive can be purchased for about £10, or £15 pounds whereas the cheapest ZIP drive is priced between £100 - £130 inclusive of VAT. You do, of course, get the floppy drive free when you purchase a computer.

Other Potable Drives

Zip Drives

Iomega 'ZIP' Drives are new developments in low cost removable drives. Aimed, primarily, at the family or small business, as a way to move data around on a small "cartridge". They can store up to 200Mb of data on a cartridge and allow the user to work directly with a back-up copy of data if the original hard disk data is corrupted in some way. It can be connected as an external parallel port, or SCSI device.

The drives are portable and light, allowing you to take the drive to another computer set up to receive it. Then, plug it in to the computer,s parallel port, or SCSI chain, and carry on using the data directly from the drive. If the other computer already has a 'ZIP'drive fitted you can transport the cartridge, only, to it. The cartridge looks similar to the 3.5 floppy disk, but is a little thicker, and costs about £12. Iomega also provides a backup tool that allows you to copy the contents of a hard disk on to a series of Zip drive disks.

Optical Drives

Although removable Zip drives allow a large amount of stored data to be moved around, using a magnetic medium still makes them vulnerable to stray magnetic fields. Optical storage may be an option to consider and is coming down in price. Although optical storage has been a slow, write only medium (the CD-ROM for example), the latest systems are re-writable and able to be erased and re-used many thousands of times. The two main optical technologies available at present is the hybrid megneto-optical and phase-change drives. The two types of drive can be either internal or external and are priced from about £300 plus, although prices are still coming down.

The Magneto-optical(MO) disk is about the same size as a 3.5-inch floppy and able to store up to 230Mb with the larger drive able to store up to 2.6Gb. Although the data is stored on the disk magnetically it is kept secure by the use of materials that have different magnetic properties at different temperatures. Local areas of the disk are heated by a laser and data written to, or read, from them. Once the area cools the data cannot be changed unless reheated or exposed to a high intense magnetic field, unlikely outside of a physics laboratory.
On the right is the Fujitsu 2512 MO Drive priced at about £300.

Developed by Panasonic, Phase-change disks (PD) allow data to be written to, and from, the disk using a single laser.
To write data, the laser heats the disk changing the optical properties of its surface. To read back the data the laser is again used, but at a lower setting. The disks can be written to at least half-a-million times and should last about thirty years. The PD disk can be formatted using the PC's standard disk function.
On the left is the Panasonic LF 1000 PD Drive priced at about £400

Hard Drives
CD-ROM Drives