Cartesian coordinates

AutoCAD follows the Cartesian coordinate system, which is a graphical method of assigning coordinates to a point in space. The simple three-dimensional space has three coordinates, namely X, Y, and Z, which are mutually perpendicular to each other, as in the following diagram. The point of intersection of the three mutually perpendicular axes is the origin, which is represented as (0,0,0):

The position of any point in a three-dimensional space can be specified using these three axes, which are represented by the X, Y, and Z axes in the preceding diagram. But for a two-dimensional space, we only need to use the X and Y axes to define the position of any point.

In a two-dimensional space, the simple (X,Y) coordinate system is used and any point in a two-dimensional space can be defined using these two coordinates only. Take the example of the following graph. Here, the origin is mentioned as (0,0), which is also the point of intersection of the X and Y axes, represented by horizontal and vertical lines, respectively:

The A (7,8) point is at 7 units from the origin along the X axis and at 8 units along the Y axis. Similarly, the B (-6,3) point is at 6 units along the negative side of the X axis and at 3 units along the positive side of the Y axis. In the case of the C (4,-5) point, the distance from the positive side of the X axis is 4 units, and its distance along the negative side of the Y axis is 5 units.

The X axis points to the right of the origin are positive and the points to the left of the origin are negative. Similarly, on the Y axis, the points on top of the origin are positive and the points below the origin are negative.