Main Memory Organization: Stored Program
The present day digital computers are based on stored-program concept introduced by Von Neumann. In this stored-program concept, programs and data are stored in separate storage unit called memories.
Central Processing Unit, the main component of computer can work with the information stored in storage unit only.
In 1946, Von Neumann and his colleagues began the design of a stored-program computer at the Institute for Advanced Studies in Princeton.This computer is referred as the IAS computer.
The structure of IAS computer is shown in the next page.
The IAS computer is having three basic units:
Central Processing Unit:
This is the main unit of computer, which is responsible to perform all the operations. The CPU of the IAS computer consists of a data processing unit and a program control unit.
The data processing unit contains a high speed registers intended for temporary storage of instructions, memory addresses and data. The main action specified by instructions are performed by the arithmatic-logic circuits of the data processing unit.
The control circuits in the program control unit are responsible for fetching instructions, decoding opcodes, controlling the information movements correctly through the system, and providing proper control signals for all CPU actions.