Commands are the instructions that tell the program what to do.
The dockable, resizable command window accepts commands and system variables and displays prompts that help you complete a command sequence (including commands that were initiated at another location such as the ribbon).
After you enter a command, you may see a series of prompts displayed at the command line. For example, after you enter PLINE and specify the first prompt, the following prompt is displayed:
PLINE Specify next point or [Arc Halfwidth Length Undo Width]:
In this case, the default is to specify the next point. You can either enter X,Y coordinate values or click a location in the drawing area.
To choose a different option, click the option. If you prefer to use the keyboard, specify the option by entering the capitalized, colored letter. You can enter uppercase or lowercase letters. For example, to choose the Width option, type w and press Enter.
Sometimes the default option (including the current value) is displayed after the angle-bracketed options:
POLYGON Enter number of sides <4>:
In this case, you can press Enter to retain the current setting (4). If you want to change the setting, type another number and press Enter.
By default, the name of a command or system variable is automatically completed as you type it. A suggestion list of commands and system variables that use the same letters is also displayed. You can control the settings for these features in the Input Search Options dialog box.
If the automatic completion features are turned off, type a letter on the command line and press the Tab key to cycle through all the commands and system variables that begin with that letter. Press Enter or Spacebar to start the command or system variable.
Some commands have abbreviated names, or command aliases, that you can enter at the command line. For example, instead of entering circle to start the CIRCLE command, you can type c and press Enter. The command Suggestion List (if displayed) indicates the alias in front of the command name: C (CIRCLE)
Command aliases are defined in the acad.pgp or acadlt.pgpfile.
Many commands can be used transparently. That is, they can be entered on the command line while you use another command. Commands that do not select objects, create new objects, or end the drawing session usually can be used in this way.
To use a command transparently, enter an apostrophe (') before entering the command at any prompt. On the command line, double angle brackets (>>) precede prompts that are displayed for transparent commands. After you complete the transparent command, the original command resumes. In the following example, you turn on the grid and set it to one-unit intervals in the middle of the LINE command.
Command: line
Specify first point: 'grid
>>Specify grid spacing (X) or [ON/OFF/Snap/Major/aDaptive/Limits/Follow/Aspect] <0.5000>: 1
Resuming LINE command
Specify first point:
Changes made in dialog boxes that you have opened transparently cannot take effect until the interrupted command has been completed. Similarly, if you reset a system variable transparently, the new value cannot take effect until you start the next command.
You can change the settings for these options from the command line Customization button or shortcut menu.