Basic Microprocessor Terminology



  • 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 2\(^8\) = 256 different locations. The locations in hexadecimal format can be written as 00H – FFH.

  • Data Bus: The data bus is used to transfer data between memory and processor or between I/O device and processor. For example, an 8-bit processor will generally have an 8-bit data bus and a 16-bit processor will have 16-bit data bus.

  • Control Bus: The control bus carry control signals, which consists of signals for selection of memory or I/O device from the given address, direction of data transfer and synchronization of data transfer in case of slow devices.


Solved Example:


8085 is a/an ______ -bit processor. (LMRC SCTO (Electronics) 2018)

Correct Answer: A

Solved Example:


Which of the following is a 16-bit register in 8085 processor? (ISRO (VSSC) Technical Assistant Electronics 2019)

  1. Stack pointer
  2. Program counter
  3. Accumulator

Correct Answer: D