1. A data processing system comprising: first address means for storing a first address signal component; second address means for storing a second address signal component; calculation means having a first input connected to said first address means and a second input connected to said second address means, said calculation means operative to produce output signals based upon the value of the data supplied to said first and second inputs; test means connected to receive said output signals from said calculation means, said test means operative to generate first and second enabling signals dependent upon the status of said output signals; transfer means connected to receive a first output signal from said calculation means and responsive to said first enabling signal from said test means for transferring said first output signal through said transfer means directly; and processing means connected to receive a second output signal from said calculation means and responsive to said second enabling signal for further processing the data on said first and said second inputs of said calculation means, and producing a further output signal as the result of the further processing.