Computer Organization and Architecture

• Computer Architecture


  is concerned with the way hardware components are connected together to form a computer system
• Computer Organization


  is concerned with the structure and behavior of a computer system as seen by the user
• Electronic Numerical Integrator and Computer


  ENIAC
• ENIAC


  was the first computing system designed in the early 1940s. It consisted of 18,000 buzzing electronic switches called vacuum tubes, 42 panels each 9'x 2'x1'. It was organized in U-Shaped around the perimeter of a room with forced air cooling. It was based on Stored Program Concept in which machine use memory for processing data
• computer organization


  describes the functions and design of the various units of a digital system
• general-purpose computer system


  is the best-known example of a digital system. Other examples include telephone switching exchanges, digital voltmeters, digital counters, electronic calculators and digital displays
• Computer architecture


  deals with the specification of the instruction set and the hardware units that implement the instructions
• Input unit, Central Processing Unit, Memory unit, Arithmetic & logical unit, Control unit, and Output unit


  A computer consists of five main components namely
• Input units


  are used by the computer to read the data. The most commonly used input devices are keyboards, mouse, joysticks, trackballs, microphones, etc.
• Central processing unit


  can be referred as an electronic circuitry within a computer that carries out the instructions given by a computer program by performing the basic arithmetic, logical, control and input/output (I/O) operations specified by the instructions.
• The Memory unit


  can be referred to as the storage area in which programs are kept which are running and that contains data needed by the running programs.
• RAM and ROM


  The most common examples of primary memory are
• Read Only Memory


  ROM
• Random Access Memory


  RAM
• RAM


  It is also known as the volatile form of memory, means when the computer is shut down, anything contained in ___ is lost
• Cache memory


  is also a kind of memory which is used to fetch the data very soon. They are highly coupled with the processor
• Secondary memory


  is used when a large amount of data and programs have to be stored for a long-term basis. The most common examples are magnetic disks, magnetic tapes, and optical disks
• ROM


  It is also known as the Non-volatile memory form of memory, means the data is stored permanently irrespective of shut down
• Arithmetic and Logical Unit


  Most of all the arithmetic and logical operations of a computer are executed in the ___ of the processor. It performs arithmetic operations like addition, subtraction, multiplication, division and also the logical operations like AND, OR, NOT operations.
• control unit


  is a component of a computer's central processing unit that coordinates the operation of the processor. It tells the computer's memory, arithmetic/logic unit and input and output devices how to respond to a program's instructions
• control unit


  is also known as the nerve center of a computer system
• Output devices


  are pieces of equipment that are used to generate information or any other response processed by the computer. These devices display information that has been held or generated within a computer
• program counters, instruction registers, memory address registers, and memory and memory data registers


  The special function registers include
• Program counter


  is one of the most critical registers in CPU. It monitors the execution of instructions. It keeps track on which instruction is being executed and what the next instruction will be
• instruction register


  is used to hold the instruction that is currently being executed. It's contents are available to the control unit, which generate the timing signals that control, the various processing elements involved in executing the instruction
• MAR and MDR


  The two registers ___ and ___ are used to handle the data transfer between the main memory and the processor
• memory address registers


  holds the address of the main memory to or from which data is to be transferred
• memory data registers


  contains the data to be written into or read from the addressed word of the main memory
• Polling


  enables the processor software to check each of the input and output devices frequently. During this check, the processor tests to see if any devices need servicing or not
• Interrupt method


  provides an external asynchronous input that informs the processor that it should complete whatever instruction that is currently being executed and fetch a new routine that will service the requesting device
• Stored Program Control Concept and Flynn's CLassification of Computers


  In Computer Architecture, the General System Architecture is divided into two major classification units
• Von-Neumann Model, General Purpose System, Parallel Processing


  Store Program Control Concept can be further classified in three basic ways:
• Stored Program Control Concept


  refers to the storage of instructions in computer memory to enable it to perform a variety of tasks in sequence or intermittently
• MJ Flynn


  proposed a classification for the organization of a computer system by the number of instructions and data items that are manipulated simultaneously
• instruction stream


  The sequence of instructions read from memory constitutes an
• data stream


  The operations performed on the data in the processor constitute a
• Registers


  are a type of computer memory used to quickly accept, store, and transfer data and instructions that are being used immediately by the CPU
• Processor registers


  registers used by the CPU are often termed as
• processor register


  may hold an instruction, a storage address, or any data (such as bit sequence or individual characters).
• Temporary Register


  is used for holding the temporary data during the processing