A computer graphic interface allows a user to obtain descriptive information concerning a feature of a displayed image by pointing to the location of the feature. Conversely, the user may enter descriptive textual information, and the locations of responsive features are indicated. The data processing and memory storage requirements are minimized by encoding information about the image as a pixel bit map, and a color map in which the addresses or indices of the color map are correlated with the addresses or pointers to strings of descriptive information. Each color map address corresponds to a predefined set of features and descriptive information about those features. Since the pixel bit map defines a color map address for each location on the image, suitable programming of the color map can insure proper correlation of descriptive information with corresponding locations on the image. The correlation between color map addresses and the descriptive information about the features is represented most compactly by arranging or sorting the entries in the color map so that there is a correspondence between each predefined feature and a continuous range of color map addresses. Therefore, for a specified color map address, the corresponding set of features and their pointers can be found by comparing the specified color map address to the limits of the color map address ranges for the various features.