An electrostatic matrix printer has a movable print head (1) in which a row of selectively energizable needles (2) is fixed for printing dots on a surface to be printed by selective energization of the needles in response to binary coded electrical signals having a number of bits, equal or less than the number of needles in the row. The binary signals, as well as determining the state of a group of consecutive needles in the row, to print different character columns, also include at least one further bit which determines the position of the said selected group of needles in the row, enabling characters of different height and vertical position to be printed.