Back in the heyday of the IBM XT, AT, and PS/2 systems the friendly and informative POST error codes we see from our modern, Plug 'N' Pray, user-friendly BIOSes were mostly nonexistent. Since ROM and RAM space were fairly limited, IBM used a solution for somewhat verbosely reporting hardware errors found by the POST (as well as some while the system was running). Each possible type of error had a number. I have not been blessed with the opportunity to work on many PCs using this system, however, I am familiar with one dreaded code:

1701 - Hard Disk Failure

Of course, the system did not explain it to you in plain Engrish as I have... you would merely switch on your computer in the morning, to find your screen black and lifeless, displaying only the dreaded numbers, 1701. The system's failure to boot, or its eventual emergence in PC-BASIC, also let you know what was wrong. Thoughts of hours, weeks, even years of lost work flashed through your mind, as you slipped into panic.

Fortunately, the dreaded 1701 was often caused by stiction, which was fairly easy to remedy and get your system back up and running.

The latest BIOS I saw the 1701 error code used on was actually an American Megatrends 80486 model. After this, it was replaced with a far more (less??) friendly "Primary (Secondary?) Hard Disk Failure" or "Hard Disk Controller Failure".