PRINTER ENABLING PRINTING AT DOUBLE SPEED AND DENSITY

PURPOSE:To enable a virtual double-density printing at a double speed through using a head having the conventional response frequency by trimming the subsequent dot when two dots are turned ON continuously in the horizontal way. CONSTITUTION:A data is fed to a print buffer 2 from a host computer 1 and a printing starts when the buffer fills to the capacity. The data at the address as specified is taken out by a print buffer addressing means 21, the immediately preceding data stored in a memory section 25 is inverted by an inversion means 23 and ORing is done between this data and the data pertaining to the current printing by a ORing execution means 22. Then, the results are stored into the memory section 25 and a printing is performed by a printing means 24. A printing position deciding means 27 is provided to decide on the printing position. When the printing position is determined to be the head of one line, the memory section is zero cleared by a memory section clearing means 26 before the invertion of the contents of the memory section 25. With such an arrangement, a virtual double-density printing can be done at the speed doubling that of the conventional double-density printing without varying the response frequency of the head.