ems having limited number of resources are called microcomputers. Nowadays, microprocessor can be seen in almost all types of electronics devices like mobile phones, printers, washing machines etc. Microprocessors are also used in advanced applications like radars, satellites and flights. Due to the rapid advancements in electronic industry and large scale integration of devices results in a significant cost reduction and increase application of microprocessors and their derivatives. Fig.1 Microprocessor-based system  Bit: A bit is a single binary digit.  Word: A word refers to the basic data size or bit size that can be processed by the arithmetic and logic unit of the processor. A 16-bit binary number is called a word in a 16-bit processor.  Bus: A bus is a group of wires/lines that carry similar information.  System Bus: The system bus is a group of wires/lines used for communication between the microprocessor and peripherals.  Memory Word: The number of bits that can be stored in a register or memory element is called a memory word.  Address Bus: It carries the address, which is a unique binary pattern used to identify a memory location or an I/O port. For example, an eight bit address bus has eight lines and thus it can address 28 = 256 different locations. The locations in hexadecimal format can be written as 00H – FFH.