Abstract: An electronic calculator or microprocessor system of a type preferably having keyboard input and the visual display is implemented with a semiconductor chip having an arithmetic unit, an address register responsive to the input, an instruction word memory for storing a number of instruction words and addressable in response to the address stored in the address register and an, instruction word decoder circuit for decoding instruction words outputted from the instruction word memory and for controlling the arithmetic unit in response thereto. An indirect addressing system includes an auxiliary register coupled to the output of the arithmetic unit for storing at least a portion of a word of numeric data outputted by the arithmetic unit and a branch logic system responsive to the decoding of a particular instruction word by the instruction word decoder logic for causing the address register to branch to a location defined by the contents of the auxiliary register.