PRINTER CONTROLLER FOR HARD COPY OF CRT SCREEN

PURPOSE:To display a waveform without using a special printer by using a conventional printer having a graph mode, reading the content of a video memory and using a dot pattern to print out waveform information in the graph mode. CONSTITUTION:The video information for patterns' share displayed on a CRT is stored in the video memory 1 and a read means 2 reads the video information of the video memory 1. A preceding bit storage means 3 stores the video information read at one preceding information among the video information of the video memory 1 read by the read means 2. A converting means 4 compares an output of the preceding bit storage means 3 with the video information read by the read means 2 and when the results of comparisor are dissident, that is, in case of [01] or [10], a line ''1'' is outputted to draw a leading line or a trailing line. When the results of comparison are coincident, that is, in case of [11] or [00], it is checked that the value is logical 1, and when the value is logical 1, an upper side point to draw a line at the upper side and when logical 0, the lower side point to draw a line at the lower side is outputted.