RELATIVE RECTANGULAR COORDINATES:

A RELATIVE RECTANGULAR COORDINATE allows you to specify a position along the X-axis, Y-axis, and Z-axis (if needed) to locate a point relative to the last point you specified.

To locate a point using the Relative Rectangular Coordinate system, type @ and then the X-value, Y-value, and, if needed, the Z-value, separated by commas and no spaces.

Example:
If your last point was at 12,8 (see FIGURE below), you can type @11,7 and AutoCAD will locate an entity or point 11 along the x axis and 7 along the y axis from the 12,8 point.

The equivalent absolute coordinate of @11,7 would be 23,15 or 12+11 on the X-axis, and 8+7 on the Y-axis.