Tài liệu AutoCAD Basics - Unit Types

If you are using engineering or architectural units, AutoCAD displays partial inches
differently than the format you must use to type them in. You must type coordinates
without any spaces because AutoCAD interprets a space as equivalent to
pressing the Enter key and ends your input. Use a hyphen between whole and
partial inches, for example, 3'2-1/2. (You can omit the after the inches because
AutoCAD assumes inches in engineering and architectural units if no symbol follows
a number.) However, this appears on the status line as 3'-2 1/2. This can be
confusing because the hyphen is in a different place, and AutoCAD inserts a space
between the whole and partial inches.
Setting the drawing units
Once you know the units you want to use, you set them in the Drawing Units dialog
box. To set the units, choose Format➪Units to open the Drawing Units dialog box,
shown in Figure 5-1. The left side of the Drawing Units dialog box enables you to
choose which unit type you want to use. In the Precision box in the Length section,
click the arrow and a list of precision options drops down. Click the one you want