IN THIS CHAPTER
Working with absolute, relative, and polar coordinates
Using direct distance entry, orthogonal mode, and polar tracking
Using snap settings
Working with object snaps
Specifying points in a drawing is one of the most fundamental tasks you do in AutoCAD and AutoCAD LT. Unless you know how to specify a point, you can't draw anything real, whether a house or a gasket. Most objects you draw have a specific size, and you need to specify that information. You draw lines, arcs, and circles by specifying the coordinates of points on the screen. As with most tasks, AutoCAD and AutoCAD LT offer many ways to accomplish this.
AutoCAD and AutoCAD LT work the same way as the graphs with X and Y axes that you plotted in high school. Look at the User Coordinate System (UCS) icon shown in Figure 4.1.
The X arrow points along the X axis in the positive direction. This means that as you go in the direction of the arrow, the X coordinates increase. The Y arrow points along the Y axis in the positive direction. Using this system, every 2D point on the screen can be specified by using X and Y coordinates. This is called a Cartesian coordinate system. The universal convention is to place the X coordinate first, and then a comma (but no space), and then ...