Stories
Slash Boxes
Comments

SoylentNews is people

PC DOS 1.1 Boot Sector Junk Identified

posted by janrinok on Saturday January 08 2022, @08:10PM   Printer-friendly
from the PC-introns dept.

owl writes:

https://www.os2museum.com/wp/unidentified-pc-dos-1-1-boot-sector-junk-identified/

Anyone trying to disassemble the PC DOS 1.1 boot sector soon notices that at offsets 1A3h through 1BEh there is a byte sequence that just does not belong. It appears to be a fragment of code, but it has no purpose in the boot sector and is never executed. So why is the sequence of junk bytes there, and where did it come from?

The immediate answer is "it came from FORMAT.COM". The junk is copied verbatim from FORMAT.COM to the boot sector. But those junk bytes are not part of FORMAT.COM, either. So the question merely shifts to "why are the junk bytes in FORMAT.COM, and where did they come from?"

It is not known if anyone answered the question in the past, but the answer has been found now, almost 40 years later—twice independently.

Original Submission

 
This discussion has been archived. No new comments can be posted.
PC DOS 1.1 Boot Sector Junk Identified | Log In/Create an Account | Top | 14 comments | Search Discussion
Display Options Threshold/Breakthrough Mark All as Read Mark All as Unread
The Fine Print: The following comments are owned by whoever posted them. We are not responsible for them in any way.

  • (Score: 2, Funny) by Anonymous Coward on Sunday January 09 2022, @04:17AM (1 child)

    by Anonymous Coward on Sunday January 09 2022, @04:17AM (#1211188)

    This is breaking news, and it came just in time. I was planning to upgrade my trusty 8088 to one of those new 80286 processors. Not sure if this release of DOS will run on the new hardware though...

    Starting Score:    0  points
    Moderation   +2  
       Funny=2, Total=2
    Extra 'Funny' Modifier   0  
    Total Score:   2  

  • (Score: 2) by Thexalon on Sunday January 09 2022, @11:44PM

    by Thexalon (636) on Sunday January 09 2022, @11:44PM (#1211347)

    Why would you do that? We all know that 640Kb should be enough for anybody!

    --
    The only thing that stops a bad guy with a compiler is a good guy with a compiler.