1. A computer aided coordinate digitizing system for use in making construction estimates, comprising: a digitizing device for determining a series of X-Y coordinate positions on a flat surface, comprising pointer means for placing at selected positions on the flat surface and sensor means for detecting the position of said pointer means and generating a series of X-Y coordinate data positions relative to selected positions on construction drawings placed on the flat surface corresponding to positioning of said pointer means at the selected positions; a computer associated with said digitizing device and linking means for allowing said computer to receive said coordinate signals, said computer having memory means for storing program instructions and said coordinate signals, said program instructions including means for using said X-Y coordinate data positions to calculate a series of desired parameters relative to a structure represented on said construction drawings for generating an estimate of the cost of construction of the structure; and user operated control means for operating said system, comprising voice activated control means for recognizing voice word commands entered by a user and generating one or more computer control signals in response to each voice entered command.