Choosing Command Options

Choosing Command Options
Many commands in AutoCAD offer several options, which are often presented to you in the Command
window in the form of a prompt. This section uses the Arc command to illustrate the format
of AutoCAD’s prompts.
Usually, in a floor-plan drawing in the United States, an arc is drawn to indicate the direction
of a door swing. Figure 2.9 shows a drawing that includes other standard symbols used in
architectural-style drawings.



Here, you’ll draw the arc for the door you started in the previous exercise:
1. Click the Arc tool in the 2D Draw control panel. The prompt Specify start point of arc
or [Center]: appears, and the cursor changes to Point Selection mode.
Examine this Specify start point of arc or [Center]: prompt. The start point contains
two options. The default option is the one stated in the main part of the prompt. In this case,
the default option is to specify the start point of the arc. If other options are available, they
appear within square brackets. In the Arc command, you see the word Center within brackets
telling you that if you prefer, you can also start your arc by selecting a center point instead of
a start point. If multiple options are available, they appear within the brackets and are separated
by slashes (/). The default is the option AutoCAD assumes you intend to use unless you
tell it otherwise.
2. Type C↵ to select the Center option. The prompt Specify center point of arc: appears.
Notice that you had to type only the C and not the entire word Center.
TIP When you see a set of options in the Command window, note their capitalization. If you
choose to respond to prompts by using the keyboard, these capitalized letters are all you need to
enter to select that option. In some cases, the first two letters are capitalized to differentiate two
options that begin with the same letter, such as LAyer and LType.
3. Pick a point representing the center of the arc near the upper-left corner of the door (see
Figure 2.10). The prompt Specify start point of arc: appears.
4. Type @3<0↵. Metric users should type @9<0↵. The prompt Specify end point of arc or
[Angle/chord Length]: appears.
5. Move the mouse, and a temporary arc appears, originating from a point 3 units to the right
of the center point you selected and rotating about that center, as in Figure 2.10. (Metric users
will see the temporary arc originating 9 units to the right of the center point.)
As the prompt indicates, you now have three options. You can enter an angle, a chord
length, or the endpoint of the arc. The prompt default, to specify the endpoint of the arc,
picks the arc’s endpoint. Again, the cursor is in Point Selection mode, telling you it’s waiting
for point input. To select this default option, you only need to pick a point on the screen indicating
where you want the endpoint.
6. Move the cursor so that it points in a vertical direction from the center of the arc. You’ll see
the Polar Tracking vector snap to a vertical position.


7. Click any location with the Polar Tracking vector in the vertical position. The arc is now
fixed in place, as in Figure 2.10.
This exercise has given you some practice working with AutoCAD’s Command window prompts
and entering keyboard commands—skills you’ll need when you start to use some of the more
advanced AutoCAD functions.
As you can see, AutoCAD has a distinct structure in its prompt messages. You first issue a command,
which in turn offers options in the form of a prompt. Depending on the option you select,
you get another set of options, or you’re prompted to take some action, such as picking a point,
selecting objects, or entering a value.
As you work through the exercises, you’ll become intimately familiar with this routine. After
you understand the workings of the toolbars, the Command window prompts, and the dialog
boxes, you can almost teach yourself the rest of the program!