A compressed refresh buffer utilizing a random access memory is disclosed which performs a mapping between the refresh buffer and a video display screen, such that only non-zero screen areas are represented in the refresh buffer. The dot image on the video screen is divided into rectangular subarrays. If the subarray has image points plotted in it, it is designated active and the bits of each active subarray are stored in the refresh buffer. If no image points are plotted in a subarray, it is designated inactive. A row bit map is provided which includes one bit for each subarray in the row with a "one" bit representing an active subarray and a "zero" bit representing an inactive subarray. Control means including a row tag pointer memory is provided for storing a linked list of pointers associated with each active subarray in a row, each pointer pointing to the location in the random access memory of an active subarray. This control means permits dynamically updating of the information in the buffer as the image is changed and updating of the map to reflect the current status of stored subarrays. Subarrays can thus be entered or deleted from the map as their active/inactive status changes.