About System Variables and Bitcodes

System variables are settings that control how certain commands work.

Whereas commands usually initiate an activity or open a dialog box, system variables control the behaviors of commands, default values for operations, or the appearance of the user interface. They turn on or turn off modes such as Snap, Grid, or Ortho. They set default scales for hatch patterns. They store information about the current drawing or program configuration. You can use a system variable to change a setting or to display the current status. Many system variable settings can also be modified in a dialog box or on the ribbon.

Note: Some system variables accept negative values either to turn off the setting or to signify a special case. You can examine or change a system variable's setting transparently, that is, while using another command; however, new values may not take effect until the interrupted command ends.

Specifying Options with Bitcode Variables

Some system variables are controlled using bitcodes. With these system variables, you add the option values to specify a unique combination of behaviors. For example, the LOCKUI system variable provides the following bitcode values:

0 Toolbars, panels, and windows not locked
1 Docked toolbars and panels locked
2 Docked or anchored windows locked
4 Floating toolbars and panels locked
8 Floating windows locked

Thus, if LOCKUI is set to 5 (that is, 1 + 4 = 5), only docked and floating toolbars are locked. Docked, anchored, and floating windows are not locked.

Displaying a List of System Variables

Like commands, the names of system variables appear in the Suggestion List that is displayed at the Command prompt as you enter a command. The commands are displayed first. Press the Tab key to switch to the system variable list. You can set whether system variables are mixed with commands or not displayed at all in the Input Search Options dialog box.

The SETVAR command lists all the system variables in the text window or the extended prompt history. You can use an asterisk (*) as a wildcard to filter the list.