English: Block diagram of an example CPU showing data paths for ALU operand sources and result destinations. This CPU has a register file with two read ports, which allows the values stored in any two registers (or the same register) to be ALU operands. Alternatively, it allows either ALU operand to be sourced from an immediate operand (a constant value which is directly encoded in the machine instruction) or from memory. The ALU result may be written to the register file or to memory.