A processor for a tape printer enables user-generated characters each formed by dot patterns in four sizes (16.times.16 dots, 24.times.24 dots, 32.times.32 dots, 48.times.48 dots). The user generates the dot pattern of the smallest size (16.times.16 dots) and the processor automatically enlarges the generated dot pattern to tentative dot patterns in the three larger sizes which can then be modified in turn by the user. Upon completion of the modification of the second size pattern (24.times.24 dots) the processor enlarges the completed second size dot pattern to a substitute fourth size tentative dot pattern (48.times.48 dots) to incorporate the modifications of the second size dot pattern into the fourth size dot pattern and thus reduce the user modifications to the fourth size dot pattern.