INT 21 - DOS 1+ - TERMINATE PROGRAM
AH = 00h
CS = PSP segment
Notes:  Microsoft recomments using INT 21/AH=4Ch for DOS 2+
execution continues at address stored in INT 22 after DOS performs
whatever cleanup it needs to do
if the PSP is its own parent, the process's memory is not freed; if
INT 22 additionally points into the terminating program, the
process is effectively NOT terminated
not supported by MS Windows 3.0 DOSX.EXE DOS extender
SeeAlso: AH=31h,AH=4Ch,INT 20,INT 22

See also: 2126

2100 - DOS 1+ - TERMINATE PROGRAM