A method of interpreting handwritten data inputted on a printed form using an optically sensing pen. The form has a plurality of different form fields for the handwritten data input. The form also includes a plurality of printed tags and the method includes the steps of: (a) receiving, from the pen, digital ink representing handwritten data input of the pen relative to the form; (b) identifying the form field in which handwritten data has been inputted; (c) identifying a set of predetermined text values associated with the identified form field; and (d) interpreting the handwritten data by decoding the digital ink and converting the decoded digital ink into computer text. The computer text is selected only from the set of predetermined text values.