Off-Line

Processing or peripheral operations performed while disconnected from the system CPU via the system bus.

 

On-Line

Processing or peripheral operations performed while disconnected from the system CPU via the system bus.

 

Open Loop Servo

A head positioning system that does not use positional information to verify and correct the radial location of the head relative to the track. This is usually achieved by use of a stepper motor which has predetermined stopping point that corresponds to track locations.

 

Operating System

A software program that organizes the actions of the parts of the computer and its peripheral devices. (See disk operating system.)

 

Outside Diameter

The largest radius recording track on a disk.

 

Overhead

The amount of extra activity it takes to perform a specific function. In the case of hard disk drive activity, there are several factors such as latency, settling time, servo overhead, and many others. These delays must be factored in when determining how long any read, write, or seek may take.

 

Overwrite

A test that measures the residual 1F recorded frequency on a track after being overwritten by a 2F signal. Variations of the test exist.