The JavaSketchpad Quick Reference   part of the jsp.awk pages

5.1.9 UnitPoint(objRef1, num);

Defines a draggable point initially located num pixels to the right of the point specified by objRef1.

JavaSketchpad allows a unit point to be dragged only to the right of its objRef1 parent. Thus, a UnitPoint construction is a convenient way of defining a point "to the right of an origin." If you then construct a coordinate system by the Origin&UnitPoint construction, using objRef1as the origin and the constructed unit point as the coordinate system's unit, the unit point will always remain at (1, 0) regardless of where it is dragged.

See also:

5.9.1 Origin&Unit(obj1, obj2);

Defines a coordinate system centered at point obj1 with a unit length determined by the distance from obj1 to point obj2.

See also:

5.9 Constructions that create Coordinate Systems

Coordinate systems in JavaSketchpad that appear with the (default) thin formatting attribute appear as "dot paper"--lattices of regularly-spaced dots. Coordinate systems that have an explicit "thick" formatting attribute appear as "grid paper" with regularly-spaced grid lines. This DR3 release of JavaSketchpad only supports display of rectangular grids, not of polar ones.

Extracted from the JavaSketchpad Construction Grammar.