Life Without An Operating System

Resources of a computer system are usually very complicated electronc devices. The disk drive, forinstance, is a very advanced combinaton.of electromechanics and electronics.

A disk drive consists of rotating magnetic plates and a moving set of read/write heads and a parallel data interface which moves data and commands to and from a disk drive.

For proper access to a hard disk drive, the "disk write operation" should consist of the following steps:

• Which disk drive is to be written?
• Does that disk drive exist?
• Is the disk drive turned on?
• Is it rotating?
• Is it rotating at the correct speed?
• Where on the disk disk drive do we need to write the data blocks? (Cylinder, sector number).
• Are these cyl/sector numbers valid for the disk drive?
• Are those cyl/sector free to be written on?
• Are the read/write heads on the correct cylinder?
• If not, move the heads to the correct cylinder.
• etc. etc.