How to use GDP?

How to draw a point?

The ‘Point’ button can be used to construct free points, semi-free points (on straight lines or circles) as well as determining intersection points between lines, between circles or between lines and circles. Under the ‘Select’ mode, free points and semi-free points can be dragged.

How to draw a straight line?

Straight lines can be constructed using the ‘Segment’ button. By double-clicking the ‘Segment’ button, we get the ‘Ray’ and ‘Line’ buttons.

How to draw a circle?

The ‘Circle’ button can be used to construct circles. This can be done by fixing a centre and a point on the circumference. These points can be given points or new points.

How to label points, lines and circles?

Using the ‘Label’ button, the positions of the labels can be adjusted. The labels can be renamed by double-clicking on them.

List of objects

The ‘Object List’ button can be used to show (or hide) the list of objects.


  1. Hold the ‘Shift’ key to select more than one objects at the same time.
  2. Press ‘H’ to hide a selected object. Another way to do this is to double-click a selected object.
  3. Press ‘Del’ to delete a selected object. Note that this will also delete all objects that have been built upon the deleted object.
  4. The arrow keys on the keyboard can serve as substitutes to the scroll bars. This may be necessary to adjust the position of the screen in the process of drawing straight lines or circles.