unless the process is its own parent (see AH=26h, offset 16h in PSP), all open files are closed and all memory belonging to the process is freed
all network file locks should be removed before calling this function
restores the terminate, Ctrl-Break, and critical error exit addresses, flushes all buffers, frees memory and returns to DOS via the termination handler address
does not close FCBs
this function is not supported in versions of DOS before 2.x, so use Int 0x21,0x00 or Int 0x20 to exit.