Computer Organization and Architecture for engineering
- 1. UNIT III COMPUTER FUNDAMENTALS
- 2. COMPUTER TYPES Embedded computers: Embedded computers are integrated into a larger device or system in order to automatically monitor and control a physical process or environment. They are used for a specific purpose rather than for general processing tasks. Typical applications include industrial and home automation, appliances, telecommunication products, and vehicles. Users may not even be aware of the role that computers play in such systems.
- 3. Personal computers: Personal computers have achieved widespread use in homes, educational institutions, and business and engineering office settings, primarily for dedicated individual use. They support a variety of applications such as general computation, document preparation, computer- aided design, audiovisual entertainment, interpersonal communication, and Internet browsing. A number of classifications are used for personal computers. Desktop computers serve general needs and fit within a typical personal workspace. Workstation computers offer higher computational capacity and more powerful graphical display capabilities for engineering and scientific work. Finally, Portable and Notebook computers provide the basic features of a personal computer in a smaller lightweight package. They can operate on batteries to provide mobility.
- 4. SERVERS AND ENTERPRISE SYSTEMS Servers and Enterprise systems are large computers that are meant to be shared by a potentially large number of users who access them from some form of personal computer over a public or private network. Such computers may host large databases and provide information processing for a government agency or a commercial organization.
- 5. SUPERCOMPUTERS AND GRID COMPUTERS N Supercomputers and Grid computers normally offer the highest performance. They are the most expensive and physically the largest category of computers. Supercomputers are used for the highly demanding computations needed in weather forecasting, engineering design and simulation, and scientific work. They have a high cost. Grid computers provide a more cost-effective alternative.
- 6. VON NEUMANN ARCHITECTURE The Von Neumann architecture, also known as the Princeton architecture, is a computer architecture based on that described in 1945 by the mathematician and physicist John Von Neumann. He described an architecture for an electronic digital computer with parts consisting of a processing unit containing an arithmetic logic unit (ALU) and processor registers, a control unit containing an instruction register and program counter (PC), a memory to store both data and instructions, external mass storage, and input and output mechanisms. The meaning has evolved to be any stored-program computer in which an instruction fetch and a data operation cannot occur at the same time because they share a common bus.
- 7. FUNCTIONAL UNITS The input unit accepts coded information from human operators using devices such as keyboards, or from other computers over digital communication lines. The information received is stored in the computer’s memory, either for later use or to be processed immediately by the arithmetic and logic unit. The processing steps are specified by a program that is also stored in the memory. Finally, the results are sent back to the outside world through the output unit. All of these actions are coordinated by the control unit. An interconnection network provides the means for the functional units to exchange information and coordinate their actions.
- 9. A program is a list of instructions which performs a task. Programs are stored in the memory. The processor fetches the program instructions from the memory, one after another, and performs the desired operations. Each instruction, number, or character is encoded as a string of binary digits called bits
- 10. INPUT UNIT Computers accept coded information through input units. The most common input device is the keyboard. Whenever a key is pressed, the corresponding letter or digit is automatically translated into its corresponding binary code and transmitted to the processor. Many other kinds of input devices for human-computer interaction are available, including the touchpad, mouse, joystick, and trackball. These are often used as graphic input devices in conjunction with displays. Microphones can be used to capture audio input which is then sampled and converted into digital codes for storage and processing. Similarly, cameras can be used to capture video input. Digital communication facilities, such as the Internet, can also provide input to a computer from other computers and database servers.
- 11. MEMORY UNIT The function of the memory unit is to store programs and data. There are two classes of storage, called primary and secondary.
- 12. PRIMARY MEMORY Primary memory, also called main memory, is a fast memory that operates at electronic speeds. Programs must be stored in this memory while they are being executed. The memory consists of a large number of semiconductor storage cells, each capable of storing one bit of information. These cells are rarely read or written individually. Instead, they are handled in groups of fixed size called words. The memory is organized so that one word can be stored or retrieved in one basic operation. The number of bits in each word is referred to as the word length of the computer, typically 16, 32, or 64 bits. To provide easy access to any word in the memory, a distinct address is associated with each word location. Addresses are consecutive numbers, starting from 0, that identify successive locations. A memory in which any location can be accessed in a short and fixed amount of time after specifying its address is called a random-access memory (RAM). The time required to access one word is called the memory access time.
- 13. CACHE MEMORY As an adjunct to the main memory, a smaller, faster RAM unit, called a cache, is used to hold sections of a program that are currently being executed, along with any associated data. The cache is tightly coupled with the processor and is usually contained on the same integrated-circuit chip. The purpose of the cache is to facilitate high instruction execution rates
- 14. SECONDARY STORAGE Although primary memory is essential, it tends to be expensive and does not retain information when power is turned off. Thus additional, less expensive, permanent secondary storage is used when large amounts of data and many programs have to be stored, particularly for information that is accessed infrequently. Access times for secondary storage are longer than for primary memory. A wide selection of secondary storage devices is available, including magnetic disks, optical disks (DVD and CD), and flash memory devices
- 15. ARITHMETIC AND LOGIC UNIT Any arithmetic or logic operation, such as addition, subtraction, multiplication, division, or comparison of numbers, is initiated by bringing the required operands into the processor, where the operation is performed by the ALU. When operands are brought into the processor, they are stored in high-speed storage elements called registers. Each register can store one word of data. Access times to registers are even shorter than access times to the cache unit on the processor chip.
- 16. OUTPUT UNIT The output unit is the counterpart of the input unit. Its function is to send processed results to the outside world. A familiar example of such a device is a printer. Most printers employ either photocopying techniques, as in laser printers, or ink jet streams. Such printers may generate output at speeds of 20 or more pages per minute. However, printers are mechanical devices, and as such are quite slow compared to the electronic speed of a processor. Some units, such as graphic displays, provide both an output function, showing text and graphics, and an input function, through touchscreen capability. The dual role of such units is the reason for using the single name input/output (I/O) unit in many cases.
- 17. CONTROL UNIT The memory, arithmetic and logic, and I/O units store and process information and perform input and output operations. The operation of these units must be coordinated in some way. This is the responsibility of the control unit. The control unit is effectively the nerve center that sends control signals to other units and senses their states. Control circuits are responsible for generating the timing signals that govern the transfers and determine when a given action is to take place. Data transfers between the processor and the memory are also managed by the control unit through timing signals.
- 18. INTERCONNECTION NETWORKS Networks interconnect whole computers allowing computer users to extend the power of computing by including communication. Advantages of networks: Communication Resource sharing Non local access Networks vary in length and performance, with the cost of communication increases with the speed and distance.
- 19. The most popular type of network is the Ethernet, which consist of LAN and WAN A local area network (LAN) is a collection of devices connected together in one physical location, such as a building, office, or home. A wide area network (WAN) is a geographically distributed telecommunications network that interconnects multiple local area networks (LANs).
- 20. The operation of a computer can be summarized as follows: The computer accepts information in the form of programs and data through an input unit and stores it in the memory. Information stored in the memory is fetched under program control into an arithmetic and logic unit, where it is processed. Processed information leaves the computer through an output unit. All activities in the computer are directed by the control unit. All the devices as connected by means of interconnected network