1 Type L and then press Enter.AutoCAD starts the Line command and displays the following prompt in the command line:LINE Specify first point:

      2 Click a point anywhere in the drawing area.The command line prompt changes toLINE Specify next point or [Undo]:

      3 Click another point anywhere in the drawing area.AutoCAD draws the first line segment.

      4 Click a third point anywhere in the drawing area.AutoCAD draws the second line segment and prompts you:LINE Specify next point or [Close Undo]:

      5 To activate the Undo option, type U and press Enter.You can type the option letter in lowercase or uppercase.AutoCAD undoes the second line segment.If you type an option that the command line doesn’t recognize (for example, X isn’t a valid option for the Line command), the command line displays an error message and prompts you again for another point — in this case, a point for the Line command:Point or option keyword required.Specify next point or [Undo]:Option keyword is programmer jargon for letters, shown in uppercase, that activate a command option. This error message is AutoCAD’s way of saying, “Huh? I don’t understand what you mean by typing X. Either specify a point or type a letter that I do understand.”

      6 Type 3,2 (with no spaces) and press Enter.AutoCAD draws a new line segment to the point whose X coordinate is 3 and Y coordinate is 2.

      7 Click several more points anywhere in the drawing area.AutoCAD draws additional line segments.

      8 Type C and then press Enter.The C instructs AutoCAD to draw a final line segment, which creates a closed figure and ends the Line command. A blank command line returns, indicating that AutoCAD is ready for the next command:Type a command

       Display the much larger text window. The normal one-line command line usually shows you what you need to see, but occasionally you want to review a larger chunk of command-line history. Press F2 to see the AutoCAD text window, which is simply an enlarged, scrollable version of the command line, as shown in Figure 2-9, left.Press Ctrl+F2 to see the editable version, as shown in Figure 2-9, right. In this mode, you can copy and paste command history. Question: How do you think I make sure that all my examples and exercises work properly? Answer: I have an excellent technical editor who checks everything.

       Press Esc to bail out of the current operation. Sometimes, you might get confused about what you’re doing in AutoCAD or what you’re seeing in the command line. If you need to bail out of the current operation, press Esc one or more times until you see a command line that has only “Type a command.” This indicates that AutoCAD is resting, waiting for your next command.

       Press Enter to accept the default action. Some command prompts include a default action in angled brackets. For example, the first prompt of the POLygon command is Enter number of sides <4>:The default is four sides, and you can accept it by simply pressing Enter. (That is, you don’t have to type 4 first.)

        AutoCAD uses two kinds of brackets when it prompts.Command options appear in regular square brackets: [Close Undo]. To activate a command option, type the letter(s) that appear in uppercase and then press Enter, or click the option directly in the command line.A default value or option appears in angled brackets: <4>. To choose the default value or option, press Enter. You can also right-click and choose Enter as input to a command. Easier yet, you can use the spacebar instead of Enter, as long as you’re not entering text.

       Watch the command line. You can discover a lot about how to use the command line by simply watching it after every action you take. When you click a toolbar button or menu choice, AutoCAD displays the name of the command in the command line. If you’re watching the command line, you absorb the command names more or less naturally.

       Leave the command line in the default configuration. The command line, like most other parts of the AutoCAD screen, is resizable and movable. The default location (at the bottom of the AutoCAD screen) and size (one line in the command line and three fading semitransparent lines extending into the drawing area) work well for many people. Resist the temptation to mess with the command line’s appearance, at least until you’re comfortable with using it.

       Right-click in the command line for options. When you right-click in the command line, you see a menu with some useful choices. For example, Recent Commands shows the last six commands you ran.

       Press the up- and down-arrow keys to cycle through the stack of commands you’ve used recently. This is another handy way to recall and rerun a command. Press the left- and right-arrow keys to edit the command-line text you’ve typed or recalled.