The absolute coordinates use the X direction and the Y direction values (from the current spot to the origin) to decide a spot (a, b).

The relative coordinates use one existing spot (not the origin) as reference to define the other as (ra, b): r stands for relative coordinates; a: the value of distance between the two spots in the X direction; b: for the value of the distance between the two in Y direction.

Polar coordinates define a point with distance between the origin and the specified point, and the angle (taking the X-axis positive direction as zero, rotating counterclockwise, when to the specified point, the angle forms) as (a<α): a is for the value of distance;α is the angle value. If the relative polar coordinates is used, it shall be (ra<α).

Coordinate values like a, b may be indicated with digits or mathematical expressions such as (a*sin(α)，b*cos(α)), taking the rectangle-drawing as an example: