Microprocessor Architecture & Its Operations

By Phil Lamass

A microprocessor is the central processing unit (CPU) of a computer. It is where processing of program instructions and data occurs. A basic computer consists of a microprocessor, external memory, and input and output devices.

Architecture of a Simple Microprocessor

The following sections describe the basic components of a simple microprocessor architecture. It is closer to early microprocessors. However, it is still the foundation of today's more complex microprocessors.

Arithmetic Logic Unit

Arithmetic and logic operations take place in the ALU.


The Accumulator holds one of the operands as well as the result in operations performed by the ALU.

Program Counter (PC)

The program counter contains the memory address of the next program instruction to be executed.

Address, Data and Status Registers and Stack Pointer

The Address Register contains address of a memory location to be accessed.The Data Register contains the data coming from or going to memory or an I/O port.The Status Register contains information about the result of the previous ALU operation. The Stack Pointer register contains the address of the block of memory (the stack) where subroutine return addresses are stored.

Control unit

The Control Unit contains the circuitry that controls the process of fetching, decoding and executing program instructions.