Direct distance entry is one of those AutoCAD features that is often overlooked. This is rather unfortunate because it can be extremely useful and an amazing time-saver. Basically, direct distance entry enables you to draw an object, such as a line, by pointing in a particular direction with the cursor and entering a distance at the command line.
Say, for example, you wanted to draw a horizontal line with a length of 30 drawing units. Start the Line command, Draw
Line from the pull-down menu or 
from the Draw toolbar. When prompted, to specify the first point for the line, pick a point somewhere on the left side of the drawing area.
You now need to constrain the line to the horizontal. You can do this using Polar Tracking . Use the POLAR button on the status bar to turn on Polar Tracking. Usually, Polar Tracking is on by default, so you may not need to do this.
