Learning Basic Commands to Get Started - AutoCAD 2011 and AutoCAD LT 2011: No Experience Required - page 44

NOTE In the exercises that follow, the enter symbol ( ↵ ) will be used.
When I say to “type” or “enter” something, it means to type the data that fol-
lows the word type or enter and then to press the enter key ( ↵ ). For example,
rather than writing “type L and press the enter key,” I'll write “enter L ↵ .”
Finally, although I'll capitalize the names of autoCaD commands, be aware
that commands are not case sensitive and may be entered however you wish.

using Coordinates

A coordinate system consists of numbered scales that identify an initial, or base,
point and the direction for measuring subsequent points on a graph. The Cartesian
Coordinate System, named after the philosopher René Descartes, who defined the xy-
coordinate system in the 1600s, consists of three numbered scales, called the x-axis,
y-axis, and z-axis, that are perpendicular to each other and extend infinitely in each
direction. As illustrated in Figure 2.10, each pair of axes (xy, xz, yz) forms a flat plane.
Most of your time using AutoCAD will be spent drawing in the xy-plane.

Z Axis
+

Y Axis

+

-

Orgin

-

+
X Axis

-

FiGuRE 2.10 The x-, y-, and z-axes and the related xy-, xz-, and yz-planes

The point where the scales intersect is called the origin. For each axis, all values
on one side of the origin are positive, all values on the other side are negative, and
values that fall in line with the origin have a value of 0 (zero). The divisions along
the scales may be any size, but each division must be equal. The axes divide the
coordinate system into four regions called quadrants. Quadrant I is the region
above the x-axis and to the right of the y-axis. Quadrant II is the region above the
x-axis and to the left of the y-axis. Quadrant III is the region below the x-axis and
to the left of the y-axis. Quadrant IV is the region below the x-axis and to the right
of the y-axis. Most of your work in AutoCAD will be done in Quadrant I, and this is
the area shown when you first open a drawing.