When working with CAD we always operate with the real-world sizes of the objects we are designing.
Format > Units
Calls up the Units Control dialogue box (illustrated) – select Decimal units with 0 precision and Decimal Degrees with 0.0 precision and then click OK.
Format >Drawing Limits
Executes the Limits command - this is the command that defines the drawing size, in this case, in model space - notice that AutoCAD prompts you, on the Command line, to specify the lower-left corner of drawing limits.
To accept the suggested value of (0,0) as the coordinates of the lower-left corner of the drawing area - note that AutoCAD always displays suggested values in angle brackets.
To specify the upper-right corner coordinates – this represents the largest drawing area that we expect to need for this drawing - we can always change it later if necessary.
Having set the drawing limits, we now need to instruct AutoCAD to display the whole of that area on the screen. At the present moment, it is only displaying a small portion of the drawing area (about 420 x 297 units out of 20000 x 15000!) because that is the default metric drawing size when AutoCAD is shipped. You ought to check that by moving the mouse pointer around the drawing area, noting the coordinate position displayed in the status area. To display the whole sheet, proceed as follows:
Issue the command Zoom with the option All - check out the Command Window to see the way AutoCAD prompts you as you enter this command and then enters the response by itself!!
Button Tools can be programmed to execute several commands, including all the necessary responses in order to perform quite complex operations.