These commands are all built in to the command interpreter itself, and cannot be changed. Sometimes this is because they require access to internal command interpreter data structures, or modify properties of the command interpreter process itself.
Untitled Database
ASSOC
BREAK
CALL
CD, CHDIR
CLS
COLOR
COPY
DEL, ERASE
DIR
DATE
ECHO
ELSE
ENDLOCAL
EXIT
FOR
FTYPE
GOTO
IF