Program control unit - Fetches program instructions from memory, decodes them and executes them one at a time.
Arithmetic and logic unit - The ALU performs arithmetic and logical operations on data such as addition and subtraction; fixed-point and floating-point arithmetic; Boolean logic such as AND, OR, NOT, XOR; and a range of shift operations.
Registers - Fast memory locations inside the processor (or an I/O controller) that may be dedicated or general-purpose.
Internal clock - Derived directly or indirectly from the system clock.
Internal buses - Several internal buses link the control unit, the ALU and the registers.