(57) A display adapter is provided for connecting the system bus 12 (Fig. 1) of a workstation to a display means 34 (Fig. 1) having a scanned display screen. The display adapter comprises input means, including means 48, 50, 46 for receiving positioning data specifying an area on the screen within which an image is to be displayed and means 54 for receiving a stream of data items representing the image. The individual data items in the received stream 42 (Fig. 2C) define respective pels of the image and the stream is ordered to define the image line-by-line and within each line, pel-by-pel. The display adapter also comprises a display buffer 38 for storing, in display scanning sequence, data defining the pels to be displayed on the display screen, and addressing logic 44, 49, 51, 58 for computing from the positioning data, individual storage locations (Fig. 2b) in the display buffer to be addressed for individual data items in the received stream in order that the data for the individual pels of the image are stored in the display buffer in said display scanning sequence and in order that the image is displayed correctly on the display screen.
The means for receiving a stream of data items preferably comprises a multiplexer which enables the stream of data items to be selectively supplied from the system bus or from a source external to the workstation.