CENTRAL PROCESSING UNIT The accumulator "A" is an 8-bit general purpose register which is often used for storing the result of arithmetic and logical operations. It also forms one of the input operands for many of these operations. The index registers "X" and "Y" are 8-bit registers which are usually used with the indexed addressing mode of the microprocessor. Use of these registers facilitates the manipulation of tables maintained in main memory. The processor status register "P" is an 8-bit register which holds the internal state of the microprocessor and status of some arithmetic and logical operations. The above is only a brief introduction to the 65C02 CPU.
For more information, please refer to the data sheet and technical documentations published by the manufacturers. 2-3