DOS startup options

Starting with DOS 6, there are multiple startup options for the CONFIG.SYS and AUTOEXEC.BAT files. You can bypass them, decide which lines to execute or set up multiple configurations for selection at startup.

Clean Boot
You can "boot the computer clean" by bypassing the CONFIG.SYS and AUTOEXEC.BAT files. This is useful if you want to test something without any TSRs or drivers loaded. In addition, if you changed CONFIG.SYS or AUTOEXEC.BAT and the computer locks up, you can still boot from the hard disk rather than having to boot from a floppy.

To clean boot, press and release F5 as soon as the "Starting MS-DOS..." message appears on screen.

Execute a Line at a Time
If a new driver or TSR causes problems, you have the option of bypassing it at startup. This is helpful for testing purposes until you change the CONFIG.SYS file permanently. To select this option, press and release F8 as soon as the "Starting MS-DOS..." message appears. Each line in CONFIG.SYS will be displayed for confirmation. Press Y to execute or N to bypass. After CONFIG.SYS is read, you will be prompted to run AUTOEXEC.BAT in its entirety or to bypass it.

Multiple Configurations
You can create multiple configurations within the same CONFIG.SYS and AUTOEXEC.BAT files. For example, a laptop on the road often needs fewer drivers than when it is connected to its docking station at home or in the office. Multiple configurations let you select the drivers required for each situation. Sometimes there isn't enough memory to load the TSRs and drivers for all the applications in a PC, or if one TSR or driver conflicts with another, users can set up separate CONFIG.SYS and AUTOEXEC.BAT files to run different sets of software. In order to activate them before DOS 6, the current CONFIG.SYS and AUTOEXEC.BAT are renamed and the required set is given those names. DOS 6 lets you place multiple configurations in CONFIG.SYS and in AUTOEXEC.BAT and prompts you for your choice at startup.

To do this, create a menu in CONFIG.SYS that defines two or more configuration blocks. The following example simulates stand-alone and network versions of CONFIG.SYS. The optional text "Select this for..." next to the MENUITEM= lines is used by DOS as the menu option at startup. If no text is placed to the right of the line, then the name of the configuration block is used as the menu option.

The menu and configuration block headers must be enclosed in left and right brackets ([ ]).

 [menu]
 menuitem=nonet   Select this for no network.
 menuitem=net     Select this for network.
 menudefault=nonet,5 <- default to "nonet" in 5
                         seconds if no choice made

 [nonet]             <- configuration block "nonet"
 device=c:\driver1.sys  <-statements that pertain
 device=c:\driver2.sys  <-to "nonet"

 [net]               <- configuration block "net"
 device=c:\netdrivr.sys

 [common]            <- common configuration block
 files=40               <-statements that pertain
 buffers=20             <-to all configurations
 etc.

You may use an include= line in a configuration block that includes all the items in another configuration block.

Important! Be sure to put the [common] configuration block last as many install programs add lines to the CONFIG.SYS file.

CONFIGURING AUTOEXEC.BAT
You can create multiple configurations in AUTOEXEC.BAT, but they must correspond to the CONFIG.SYS configuration blocks. To do this, add the goto %config% line at the end of all common statements in AUTOEXEC.BAT; for example:

   all common lines in AUTOEXEC.BAT
   goto %config%

   :nonet             <- be sure to use colon
   all statements for "nonet"
   goto end

   :net
   all statements for "net"
   goto end

   :end               <- last line in AUTOEXEC.BAT