There are many commands that are built in to COMMAND.COM and can be executed at any time. This is the complete list for MS-DOS Version 6.22:
BREAK, CHCP, CD, CLS, COPY, CTTY, DATE, DEL, DIR, EXIT, MD, PATH,
PROMPT, RD, REN, SET, TIME, TYPE, VER, VERIFY,VOL, CALL, REM, PAUSE,
ECHO, GOTO, SHIFT, IF, FOR, LOADHIGH