In constant angular velocity (CAV) recording, in which the disk spins at a constant speed no matter where the data is written, the sectors closest to the spindle are packed tighter than the outer sectors and so require a slightly different timing to write the data in the most reliable way.
In the past, one of the hard disk parameters stored in a PC's CMOS memory was the WPcom number, a marker of the track where stronger precompensation begins, i.e. the transitions are shifted further in time.
All hard disk types in common use after the early 1990s have a drive-specific controller built into the actual drive enclosure.
Until the late 1990s, many PC BIOS setup programs still allowed the user to set WPcom numbers and other drive parameters for use with older hard disk types should the need arise; it wasn't always made very clear to the user that his more modern drive would almost certainly ignore the setting.
Since then, the WPcom number is no longer even offered as a BIOS setting any more, as it has become a fully automated and internally handled feature of disk drives.