sentences:  This is the technique of recognizing certain special shapes not as handwriting input, but as an indicator of a special command.For example, a "pig-tail" shape (used often as a proofreader's mark) would indicate a "delete" operation.Depending on the implementation, what is deleted might be the object or text where the mark was made, or the stylus can be used as a pointing device to select what it is that should be deleted.