There are three locations in the DOS where OEMs may want to
patch in information specific to their installation.


The first is the location of the default switch character.
This character is one byte at DEBUG location 1E5, and is
set to '/'. To change it to '-' (XENIX compatible)
do:

        DEBUG MSDOS.SYS

        >e1e5
        XXXX:01E5   2F.         <at this point give the desired
                                 new switch character in HEX and
                                 hit return>
        >w
        Writing YYYY Bytes
        >q

If the byte at 1E5 is not 2F, look around in the immediate
vacinity (do d1e0) for it. It is the only 2F in that area.


The second is the location of the 24 bit user number and the
8 bit OEM number. These values are returned by the GET_VERSION
system call.
The user number is 3 bytes starting at
debug location 683, The OEM number is one byte at debug location
686. The user number is initialized to 0, the OEM number to -1
and they immediatly follow the Microsoft Copyright message. If these
bytes are not zero, look for the four bytes following the
Copyright message which should be in the vacinity of 683.
OEMs should request an OEM number from Microsoft if they
want one of their very own, this prevents selecting one someone
else already has.


The third is the location of the editing template definitions.
This is a table which defines the two byte edit function keys
for system call 10 and for EDLIN. This table is at debug location
33EA, and should start with a 1B. If the byte at 33EA is not
1B, look around in the immediate vacinity. Here is what the
default table looks like. It is a definition for the Zenith
Z-19 terminal:

ESCCHAR DB      1BH     ;The Escape character, Nul (0) on IBM
ESCTAB:
	DB	"Z"	;5AH Put a ^Z in the template, F6 on IBM
        DB      "S"     ;53H Copy one char, --> on IBM
        DB      "V"     ;56H Skip one char, DEL on IBM
        DB      "T"     ;54H Copy to char, F2 on IBM
        DB      "W"     ;57H Skip to char, F4 on IBM
        DB      "U"     ;55H Copy line, F3 on IBM
        DB      "E"     ;45H Kill line, Not used on IBM
        DB      "J"     ;4AH Reedit line, F5 on IBM
        DB      "D"     ;44H Backspace, <-- on IBM
        DB      "P"     ;50H Toggle insert mode, INS on IBM 
        DB      "Q"     ;51H Toggle insert mode, INS on IBM 
        DB      "R"     ;52H Escape char, F7 on IBM
        DB      "R"     ;52H End of table, must be same as previos character