865 issued to d p darwin et al on aug 5 1975 the independent control of the paper feed and print head motors in principle enables dots to be printed in any position on the paper furthermore with the mechanism very good registration of overprinted dots is possible in addition to the normal character sets based on an eight high seven wide dot pitch cell the printer can print graphics and also half tone images using digital half toning techniques the printer is particularly suited to graphics since all electromechanical functions of the mechanism can be put under program control a description of a printer control is to be found in u s pat no 4 096 758 issued to c d malkemes on june 20 1978 finally a complete description of the ibm 5103 printer is to be found in ibm 5103 printer maintenance manual form no sy31 0414 the modification to the printer mechanism to enable it to operate as a multi colour printer involves replacing the monochrome ribbon with a wide multi colour ribbon each colour of which is provided as a longitudinal stripe along the entire length of the ribbon and adding a ribbon vertical shift mechanism to selectively bring the various colours into alignment with the print element of the print head the ribbon shift mechanism is operated under program control and by overprinting using different colour stripes on the ribbon in addition to the direct printing with the individual ribbon colours themselves a wide range of different colours are available for colour graphics and colour image reproduction the operation of the vertical shift mechanism could be.