A line printer attachment (100) for converting a display screen terminal to a line printer. The last or extra line of the display is used as the line print buffer. An initiate print signal is generated upon detecting that the last or extra line is to be scanned. The initiate print signal is used to blank or inhibit the serial video data from the display screen (40) and to enable the printer (300). The serial video data is constantly sent to the printer attachment but is ignored until the printer is enabled. With the printer enabled, printing takes place using the line print buffer data which has been serialized as serial video data. The print buffer data remains unchanged during the entire printing of the line where the printing is done in series of horizontal lines to complete the printing of a iine. At the end of each horizontal line of print a vertical screen retrace occurs and the display screen is swept where again the last or extra line is detected and another initiate print signal is generated. The next horizontal line of the series of horizontal lines for completing a line of print is printed and the operation repeats until an entire line of printing is completed.