VSOEM is a utility to make a correlation between VESA and OEM SVGA video modes.
Just run it from the DOS command line (there aren't any command line arguments)
and it will output the text file VSOEM.COR.  On the off-chance that it's not
clear why you might need this utility, I'll add a little explanation.  SVGA
video modes can generally be put into two different classes.  The "standard"
ones (in the sense that they can be accessed via standard bios calls) need a
maximum of 7 bits to specify the video mode and are often called "OEM modes."
(An OEM mode integer is always less than 128.)  VESA video modes, also called
"15-bit modes," require anywhere between 9 and 15 bits.  (A VESA mode integer is
always greater than 255.)  When your video adapter is being accessed via bios
calls (as opposed to direct hardware access), various functions associated with
interrupt 10h are used.  For example, for OEM video modes function 0 sets
the mode and function Fh returns the value for whatever the current mode is.
Interrupt 10h is also used for VESA modes but the function changes.  VESA
bioses are always accessed via function 4Fh.  Hence, if you use function 4Fh
to set a 15 bit video mode, function Fh isn't likely to return the same value
function 4Fh used to set it.  Function Fh is going to return the 7-bit integer
that your video adapter thinks is the mode it's in.  This is what VSOEM does.
It uses the VESA bios call to set a VESA mode, for each VESA mode that you have
support for, and then it uses a call to your standard bios to see what *it*
thinks the video mode is.  Why do you care?  Well, there's a very understandable
chance that you don't.  However, if like me, you have applications that insist
on making you specify the video mode to get the particular screen resolution
that you want, and that application won't let you specify a VESA mode integer,
VSOEM's results can be used to tell you what OEM mode to use.  (This assumes
you know the VESA integer that gives you what you want--you can use VS or VS1
for *that*.)  In addition to pointing out that the mode integers specified in
VSOEM.COR are in hex, I should perhaps point out that the correlation drawn
by VSOEM may not necessarily be 100% valid.  VSOEM assumes that you have at
least one OEM video mode corresponding to every VESA mode.  (You may have more
than one, but VSOEM is only going to find one of them.)  If you don't (and I
don't necessarily know that this is possible), function Fh is just going to be
"lied to" by your bios.  (Other than simply just trying the OEM mode out with
your application, I don't have a good suggestion for how to spot the lie.)

If your VESA bios is like mine and it reports support for OEM modes as well as
VESA ones, you really don't need VSOEM; you can just use VS or VS1.  (Also,
note that you can't go the other way--in case you've decided to experiment
yourself.  If you use interrupt 10 / function 0 to set an OEM mode and then
try to use VESA function 4Fh / subfunction 3 to read the video mode, thinking
that it should give the VESA equivalent, well, nice try, but all you'll get is
the 7 bit mode you initially set--VESA recognizes those modes.)
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