Introduction A microprocessor is multipurpose, programmable, clock driven, resister based electronic device that reads binary instruction from the storage device called Memory, binary data as input and process data according to those instructions and generates the result as an output. A central processing unit (CPU) built on a single chip is called a microprocessor . The microprocessor contains electronic circuits with a large number of electronic components (such as transistors, resistors etc...) integrated into a single component called chip . Evolution of Microprocessor Growth of Microprocessor has been several stages starting from 4-bit to present 64-bit processor and multi-core designs. A computer-on-a-chip is a variation of a microprocessor or which combines the microprocessor core (CPU), some memory and input/output (I/O) lines, all on a single chip. · 4- bit design · 8- bit design · 16-bit design ·