DIGITAL DATA PROCESSING SYSTEM WITH ACCUMULATOR INSREUCTIONS

A system for performing operations on data items in digital computer systems in which the instructions may not specify internal registers in the processor as destinations of data received from memory or sources of data provided to memory. The system includes a result memory, apparatus for executing operations, instructions containing operation codes which specify that the result memory is to be a source of data to be operated on by the apparatus for executing operations, and control apparatus responsive to the operation codes for controlling the apparatus for executing operations. The result memory stores only the results of previous operations and may serve only as an input to the apparatus for executing instructions. The apparatus for executing operations may receive items to be operated on from either the computer system memory or the result memory. When an operation code specifies that the apparatus for executing operations receive an input from the result register, the control apparatus causes the operation execution apparatus to select the contents of the result memory as an input. Operation codes may further specify that the result be stored in the system memory as well as in the result memory.