Debugging the Debugger (16-bit)

After checking that Vista still has old MS-DOS real mode 16-bit debug.exe with commands similar to WinDbg ones we tried to debug notepad.exe:

C:\Users\user>debug
-?
assemble     A [address]
compare      C range address
dump         D [range]
enter        E address [list]
fill         F range list
go           G [=address] [addresses]
hex          H value1 value2
input        I port
load         L [address] [drive] [firstsector] [number]
move         M range address
name         N [pathname] [arglist]
output       O port byte
proceed      P [=address] [number]
quit         Q
register     R [register]
search       S range list
trace        T [=address] [value]
unassemble   U [range]
write        W [address] [drive] [firstsector] [number]
allocate expanded memory         XA [#pages]
deallocate expanded memory       XD [handle]
map expanded memory pages        XM [Lpage] [Ppage] [handle]
display expanded memory status   XS