You can close the current drawing file without actually quitting AutoCAD by choosing Close > Current Drawing from the Application Menu or by entering CLOSE at the Command prompt. To close the current opened file or all opened files,
(i) Click on the Application button. Now Application menu appears.
(ii) Move the mouse to the Close button, then select either Current Drawing to dose the current file, or All Drawings to close all the opened files in single command.

Drawing with the line tool
1. Click the New button in the Quick Access toolbar. AutoCAD displays the Select Template dialog box.
2. Select a template file acad.dwt, and then click Open.
3. The LINE command can be activated:
a) by selecting the icon from the Draw panel
b) from the menu bar with Draw > Line
c) by entering the command at the prompt line, e.g. LINE

To save your work and remain in AutoCAD:
1. Click the Save button in the Quick Access toolbar.
2. If the drawing has not yet been named, the Save Drawing As dialog box appears.
3. Name the drawing in the File name text box, and then choose Save.

To erase an object,
(i) Start the ERASE command by choosing
(ii) Home tab > Modify panel > Erase tool. (or) Type ERASE (or) E in the Command line. Now the cursor changes from the crosshairs to a little square.
(iii) This is called the pick box.
(iv) Its appearance indicates that AutoCAD is ready for you to select objects on the screen. Also note the command line;  it's prompting you to select objects.

Ribbon control panel are the Arc and Circle buttons found in ARC toul.

By pressing ESC while an operation is in progress, it terminates the command.

(i) Creating a rectangle using the LINE command, but doing so has some disadvantages.
(ii) For example, you would have to take the time to make sure that the comer angles are exactly 90°. Also, each line segment would be a separate object.
(iii) Therefore, AutoCAD 2016 provides the RECTANG command, which allows you to create a rectangle with perfect corners and as a single object.
(iv) Clicking anywhere on a rectangle created with the RECTANG command selects the entire rectangle.

(i) The Close option is used to join the current point to the start point of the first line when two or more continuous lines are drawn.
(ii) If you specify the end point by using the mouse, then click at the start point of the first line or enter C at the Command prompt, as given in the Command prompt below.
Command: LINE
Specify first point: Pick the first point.
Specify next point or [Undo]: Pick the second point.
Specify next point or [Undo]: Pick the third point.
Specify next point or [Close/Undo]: C (The fourth point joins with the first point).

(i) If the SNAP MODE button is chosen, the, snap mode will turn ON.
(ii) When snap is on, the cursor under mouse control can only be moved in jumps from one snap point to another.
(iii) The F9 key acts as a toggle key to turn the snap off or on.

you can turn it off with the UCSICON command. Type the command name, and then enter the Off option, as follows:
(i) Command: ucsicon (Press ENTER.)
(ii) Enter an option [ON/OFF/All/No origin/Origin/Properties ]: off (Press ENTER.)

(i) Ribbon Minimized to Panels
(ii) Ribbon Minimized to Panel Titles
(iii) Ribbon Minimized to Panel Tabs

To hide all the buttons on the Ribbon the panel back to its respective tab by clicking the small button at the top right side.

To start AutoCAD 2016,
(i) double-click the AutoCAD 2016- English icon on your Desktop (or)
(ii) Click Start > All Programs > Autodesk > AutoCAD 2016 > AutoCAD 2016 - English.