The microprocessor is a program-controlled semiconductor device(IC), which fetches (from memory), decodes, and executes instructions. It is used as a CPU (Central Processing Unit) in computers.

The basic functional blocks of a microprocessor are ALU (Arithmetic Logic Unit), an array of registers, and a control unit. The microprocessor is identified with the size of data, and the ALU of the processor it can work with at a time. The 8085 processor has an 8-bit ALU, hence it is called an 8-bit processor. The 8086 processor has a 16-bit ALU, hence it is called a 16-bit processor.