control technique 34 briefly additions deletions and insertions of control codes can be accomplished in the dynamic shift register by operator keying from keyboard printer 1 as explained in detail therein the dynamic shift register memory comprises m character storage positions of n bits in width the data is continually recirculated throughout the memory in the form of a loop an n bit operation flag code is initially written into one of the storage locations while n bit dummy codes are written into the remainder of the storage locations each character or control code to be inserted into the memory is inserted into the memory location that precedes the operation flag and the remainder of character or control codes and dummy codes are shifted to accommodate the insertion in a similar manner the operation flag code may be used to define the point of output of characters and control codes from the memory thus the operation flag defines the operation point within the memory without the necessity for clocking between an input output device connected to the memory and without a complex addressing system to determine the appropriate memory locations for input or output operations codes circulated through the dynamic shift register control and decode 3 likewise are used by the adjust logic 8 which operates partially under the control of the internal adjust logic 11 as explained hereinafter the difference between adjust logic 8 and internal adjust.