A processor that can execute instructions in either scalar mode or vector mode. In scalar mode, instructions are executed once per fetch. In vector mode, instructions are executed multiple times per fetch. In vector mode, the processor recognizes scalar variables and vector variables. Scalar variables may be assigned a fixed memory location. Vector variables use different physical locations at different iterations of the same instruction. The processor includes circuitry to automatically index addresses of vector variables for each iteration of the same instruction. This circuitry partitions a register into a vector region and a scalar region. Accesses to the vector region are automatically indexed based on the number of iterations of the instruction that have been performed.