Von-Neumann Architecture: John von Neumann gave the idea of basic organization of digital computer in 1946.

  1. It contains CPU, main memory, i/p &o/p devices and secondary storage device.
  2. He gave the idea of storing programs & data in same high speed memory unit . This idea was known as stored program concept. 
  3. Main memory is used to store both data and instruction. 
  4. ALU is capable of performing arithmetic and logical operations on binary data. 
  5. Program control unit (PCU) interprets the instructions in memory  causes them to be executed.
  6. I/O unit gets operated from control unit. 
  7. The storage location of control unit and ALU are called registers. 
The various registers of this model are:-

  1. MBR(memory Buffer Register): It consists of word to be stored in memory or is used to receive a word from memory. 
  2.      MAR(Memory Address Register): it contains the address in memory of word to be written from or read into MBR.
  3. IR(Instruction Register): It contains 8-bit opcode (operation code) instruction being executed. 
  4. IBR(Instruction buffer Register): It is used to temporarily hold instruction from word in memory. 
  5. PC(Program Counter): It contains address of next instruction to be fetched from memory. 
AC(Accumulator) & MQ(Multiplier Quotient): Are employed to temporarily hold the operands & results of ALU operations.