This thesis describes the implementation of a Controlled English Commenting (CEC) system that aids a VHDL modeler in entering controlled English comments. The CEC system developed includes a graphical user interface (GUI). The interface permits a modeler to submit comments for insertion at user selected points in a text file containing the model. A submitted comment is analyzed for vocabulary and syntax, and is then inserted if it is controlled English. If it is not, the CEC system extracts all possible controlled English comments that can be formed from the original comment and presents them to the user for selection and entry into the model. The interface then queries the user to complete any residual portions of the original comment until the user is satisfied. Until the user becomes familiar with the constraints of the controlled language, significant interaction is needed, particularly on complex comments. Preliminary experiments indicate that users rapidly learn the language's constraints and the need for interactive help declines. / Master of Science