System variables are the settings that AutoCAD checks before it decides how to do something. Most system variables are controlled by the OPtions command, but you can also change the value of a system variable by simply typing its name at the AutoCAD command prompt and pressing Enter.


APERTURE controls how closely the crosshairs must be to an object before an object snap marker appears. You can set APERTURE from the command line between 0 and 50 pixels, or you can set it in the Options dialog box by adjusting the slider to a maximum of 20 pixels. The default value is 10.


DIMASSOC controls how the AutoCAD dimension objects are created. When DIMASSOC is 0, AutoCAD creates exploded dimensions of separate lines, 2D solids, and text.

When DIMASSOC=1, dimensions are referred to as nonassociative —they’re single objects, but they usually don’t update if you change the size of an object.

When DIMASSOC=2 (the default setting), AutoCAD creates fully associative dimensions. You can set this value from the command line or select the Make New Dimensions Associative check box after choosing Options→User Preferences.


When MENUBAR is 1, AutoCAD displays its traditional classic menu bar below the application title bar. If MENUBAR is set to 0 (the default), the menu bar doesn’t appear. MENUBAR is set automatically when you switch between the AutoCAD Classic and Drafting & Annotation workspaces.


You’ll frequently build up a drawing by mirroring already-drawn components of it. That’s what the MIrror command does. AutoCAD realizes that you rarely want to produce a mirror image of any text that may be included.

On the other hand, suppose that you want to draw the mold for a cast part, and the finished part has some text molded in it, such as a company name or a part number.

Simply set the MIRRTEXT system variable to 1, and the MIrror command mirrors the text. MIRRTEXT is stored in the drawing.


Say that you’re looking at a wireframe cube in Plan view and you want to draw a line between two diagonal corners on top of the cube. By using object snaps to pick the corners, you’ll often find that the line isn’t on the plane of the top of the box, but that it starts at a top corner and ends at a bottom corner.

One way around this problem is to set the OSNAPZ variable appropriately. Because OSNAPZ is set to 0 by default, AutoCAD finds the X,Y,Z coordinates of the snapped-to point — but often, you don’t want that to happen. Set OSNAPZ to 1, and AutoCAD replaces the Z value of the picked point with the current elevation or the Z value of the first point picked.


The pickbox is the little square box that the crosshairs turn into when AutoCAD prompts you to select an item. You control the pickbox size by setting a value in pixels for the PICKBOX variable. The initial setting of PICKBOX is 3, which is fine for a lower screen resolution, such as 1024 x 768. But, a higher setting might be useful for higher resolutions.


Maybe you work on a number of projects and you want a separate desktop icon for each one to start in a particular folder. If so, REMEMBERFOLDERS is your ticket to Nirvana. By default, it’s set to 1, so it defaults to storing files in my Documents in Windows XP and Windows 8.

Set this variable to 0, and it opens from, and saves to, the folder you specify in the desktop icon, and in the last folder you visit as you work. REMEMBERFOLDERS is stored in the Windows Registry.


ROLLOVERTIPS controls the tooltip-like message boxes you see when you hover the mouse pointer over objects. When ROLLOVERTIPS is set to 1, pausing the cursor on an object opens a temporary panel showing the object type with its layer, color, and linetype. If you find the panel intrusive, set its value to 0.

ROLLOVERTIPS is stored in the Windows Registry.


A tooltip is the little box that appears when you hover the mouse pointer over a toolbar or Ribbon button. Tooltips are useful when you’re getting to know your way around a program, but they can get in the way if you’re not a beginner. TOOLTIPS is set to 1, to appear whenever you hover the mouse pointer over a program element.

Set TOOLTIPS to 0 if you don’t want to see tooltips again. The TOOLTIPS setting is stored in the Windows Registry.


Sometimes, you want an xref to look different from the current drawing so that you can tell which is which. You can change the layer colors of xrefs in the Layer Property Manager. When VISRETAIN is set to 0, the layer properties in the xref take precedence, so you would have to make those changes every time you open the host drawing.

When VISRETAIN is set to 1 (the default value), changes you make to layer properties in the host drawing remain intact every time you open that host drawing; however, those changes have no effect on the external file itself. The VISRETAIN value is stored in the current drawing.

And the bonus round

Here are two system variables that are fun to use, even if they don’t boost your productivity.

Using MTJIGSTRING, you can substitute as many as ten characters of your choice to replace the usual abc prompt when you start the MText command. For example, I’m great! just fits.

This last variable is invoked slightly differently from MTJIGSTRING. Enter the following line to turn on the deprecated DOS screen menu:

(setvar “screenmenu” 1)

The DOS screen menu is fast, has no icons or tooltips, and is fully context-sensitive. No matter how you start a command, its options appear automatically.

Clicking AutoCAD always returns you to the root menu, and clicking **** opens a list of the temporary object snap overrides.