ALU: Performs arithmetic & logical operations.

Control Unit: performs instruction fetch, instruction decode & other control operations.

Registers: used for storing operands (data) & temporary results.

Flags: Remember special conditions temporarily.

Buffers / Drivers: interfaces microprocessor with external units like memory & I/O units. 

  • Microprocessor has universal feature i.e has an internal bus. 
  • All hardware functional units inside microprocessor are connected to internal bus. 
  • Hardware units use internal bus for internal communication 

  • Internal bus is used for all types of communication among the functional units viz., address, data, instruction & control.
  • Bus buffers provide sufficient driving capability to microprocessor’s address, data or control bus signals.
  • Buffers provide physical interface to external world. Eg: Microprocessor using MOS technology as internal circuits, still provide TTL compatible input/output pins using Bus Buffers.