I feel old for recognising that address and knowing the answer to the question before I even read the article...<p>You can see the actual bootloader code in the PC's BIOS here:<p><a href="http://static.pcjs.org/pubs/pc/reference/ibm/5150/techref/1981-08/pages/IBM-5150-TECHREF%20214.pdf" rel="nofollow">http://static.pcjs.org/pubs/pc/reference/ibm/5150/techref/19...</a><p>The address is mentioned in lines 44 and 45 here:<p><a href="http://static.pcjs.org/pubs/pc/reference/ibm/5150/techref/1981-08/pages/IBM-5150-TECHREF%20196.pdf" rel="nofollow">http://static.pcjs.org/pubs/pc/reference/ibm/5150/techref/19...</a><p>(It would be so very awesome if this was the sort of documentation you got if you purchased a new computer, although perhaps on a disc instead of hardcopy.)