Hard drives

The hard drive first appeared in the IBM PC/XT and stored a whopping 10 MB of data. Most people never dreamed they could ever use that much storage space. Today hard drives can store more than 9 GB of data. Almost computers on store shelves have at least 2 GB hard drives, a 4 GB hard drive is fast becoming the norm.

Hard drives in the past used either an ST-- 506 interface when EST I (enhanced small device interface) to transmit data to other parts the computer. Today's hard drives used either SCSI (small computer system interface) or IDE (integrated drive electronics) drives.

A hard drive consists of several small disks, or "platters." Data is stored on hard drives in bytes. The bytes are arranged in groups of 512 bytes, which are called sectors. Sectors are grouped together into concentric tracks tracts are sometimes referred to as cylinders, but this is a mistake. Cylinders are actually made up of a single track that runs through the platter. Tracks are circles and if you stacks circles on top of each other you get a cylinder. The number of tracks on each platter is identical to the number of cylinders on the hard drive. This is why manufacturers list information about the number of cylinders and don't usually list any track information.

Floppy drives

Floppy drives have been designed in many sizes. The first floppy drive in a PC could hold 160 bytes of data. When IBM introduced the PC/XT, it came with a 360 to a diskette drive these were called floppy drives because the diskettes that were used in the drives were very flexible eventually, a 1.2 MB diskette with this same construction was introduced. Even though the 1.2 MB looks identical to the 360 to a diskette, is constructed using different materials and stores data in a different way. You may be tempted to format a 360 K. diskette to 1.2 MB, but you'll still get several bad sectors during the format process. You should always use the appropriate to diskette to avoid data loss.

In the late 1980s, the 3.5 inch diskette was introduced. This new diskette could hold 720 K. of data this diskette also came in a harder case than previous diskettes. A spring loaded door closed over the opening in the magnetic media when the diskette was removed from the drive. Today the 3.5 inch diskettes can hold up to 2.88 MB of data, but the norm is 1.44 MB.

Expansion cards

Expansion cards, also called adapters, allow you to add devices to your PC. These devices can range from CD-ROMs to video display devices. Expansion cards. According to the bus they were designed for. The most common type of expansion card is the 16-bit I SA card.

Expansion cards plug into slots in motherboard. Most expansion cards have external connectors to attach external devices to the computer. Below is a list of some of the more common types of expansion cards: