DOS 6 provides the following enhanced configuration options:

New CONFIG.SYS commands make it possible to display an interactive
menu of configuration options.  Different sets of commands can be
executed depending upon the user input.  DOS provides a way to
specify a timed default selection and a way to continue along a
particular boot path in the AUTOEXEC.BAT file.
     At system startup, you can press F5 (or press and hold SHIFT) to
bypass the commands in CONFIG.SYS and AUTOEXEC.BAT.  This can get
you out of a tough situation in which a configuration problem is
causing a system lockup.  DOS 6.2: Ctrl+F5 also bypasses loading
     If you press F8 during system startup, you will get a chance to
step through the commands in CONFIG.SYS one-by-one, skipping any
commands that are causing a problem.  This option also lets you
bypass execution of AUTOEXEC.BAT.  DOS 6.2: Ctrl+F8 lets you
process individual commands in AUTOEXEC.BAT.

cmd?=  Place a question mark (e.g., DEVICE?=RAMDRIVE.SYS) in any
CONFIG.SYS command to be prompted whether to execute that command.

;(rem) Semicolon at the start of a line indicates a remark.

SET    With DOS 6.0+, you can create environment variables in CONFIG.SYS.

SWITCHES= (/N disables Clean Boot and Interactive Boot)
- -

Enhanced CONFIG.SYS Options