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Computer architecture and Science behind Computers



Computer architecture, Internal structure of a digital computer, encompassing the design and layout of its instruction set and storage registers. The architecture of a computer is chosen with regard to the types of programs that will be run on it (business, scientific, general-purpose, etc.). Its principal components or subsystems, each of which could be said to have an architecture of its own, are input/output, storage, communication, control, and processing.

Computer science, the study of computers, including their design (architecture) and their uses for computations, data processing, and systems control. The field of computer science includes engineering activities such as the design of computers and of the hardware and software that make up computer systems.
Since computer systems are often too large and complicated to allow a designer to predict failure or success without testing, experimentation is incorporated into the development cycle. Computer science is generally considered a discipline separate from computer engineering, although the two disciplines overlap extensively in the area of computer architecture, which is the design and study of computer systems.

Mathematics is the source of one of the key concepts in the development of the computer—the idea that all information can be represented as sequences of zeros and ones. In the binary number system, numbers are represented by a sequence of the binary digits 0 and 1 in the same way that numbers in the familiar decimal system are represented using the digits 0 through 9. The relative ease with which two states (e.g., high and low voltage) can be realized in electrical and electronic devices led naturally to the binary digit, or bit, becoming the basic unit of data storage and transmission in a computer system.

Computer graphics was introduced in the early 1950s with the display of data or crude images on paper plots and cathode-ray tube (CRT) screens. Expensive hardware and the limited availability of software kept the field from growing until the early 1980s, when the computer memory required for bit-map graphics became affordable. (A bit map is a binary representation in main memory of the rectangular array of points [pixels, or picture elements] on the screen.

Architecture deals with both the design of computer components (hardware) and the creation of operating systems (software) to control the computer. Although designing and building computers is often considered the province of computer engineering, in practice there exists considerable overlap with computer science.
Basic computer components

A digital computer (see also analog computer) typically consists of a control unit, an arithmetic-logic unit, a memory unit, and input/output units. The arithmetic-logic unit (ALU) performs simple addition, subtraction, multiplication, division, and logic operations—such as OR and AND. The main computer memory, usually high-speed random-access memory (RAM), stores instructions and data.

The control unit fetches data and instructions from memory and effects the operations of the ALU. The control unit and ALU usually are referred to as a processor, or central processing unit (CPU). The operational speed of the CPU primarily determines the speed of the computer as a whole. The basic operation of the CPU is analogous to a computation carried out by a person using an arithmetic calculator.

I/O units, or devices, are commonly referred to as computer peripherals and consist of input units (such as keyboards and optical scanners) for feeding instructions and data into the computer and output units (such as printers and monitors) for displaying results.

In addition to RAM, a computer usually contains some slower, but larger and permanent, secondary memory storage. Almost all computers contain a magnetic storage device known as a hard disk, as well as a disk drive to read from or write to removable magnetic media known as floppy disks. Various optical and magnetic-optical hybrid removable storage media are also quite common, such as CD-ROMs (compact disc read-only memory) and DVD-ROMs (digital video [or versatile] disc read-only memory).

Computers also often contain a cache—a small, extremely fast (compared to RAM) memory unit that can be used to store information that will be urgently or frequently needed. Current research includes cache design and algorithms that can predict what data is likely to be needed next and preload it into the cache for improved performance.

Linking processors
·         Multiprocessor design
Creating a multiprocessor from a number of uniprocessors (one CPU) requires physical links and a mechanism for communication among the processors so that they may operate in parallel. Tightly coupled multiprocessors share memory and hence may communicate by storing information in memory accessible by all processors. Loosely coupled multiprocessors, including computer networks , communicate by sending messages to each other across the physical links.
Computer scientists also investigate methods for carrying out computations on such multiprocessor machines—e.g., algorithms to make optimal use of the architecture, measures to avoid conflicts as data and instructions are transmitted among processors, and so forth. The machine-resident software that makes possible the use of a particular machine, in particular its operating system, is in many ways an integral part of its architecture.

·         Network protocols
Another important architectural area is the computer communications network, in which computers are linked together via computer cables, infrared light signals, or low-power radiowave transmissions over short distances to form local area networks (LANs) or via telephone lines, television cables, or satellite links to form wide-area networks (WANs).
Network protocols also include flow control, which keeps a data sender from swamping a receiver with messages it has no time to process or space to store, and error control, which involves error detection and automatic resending of messages to compensate for errors in transmission.

·         Middleware
A major disadvantage of a pure client-server approach to system design is that clients and servers must be designed together. That is, to work with a particular server application, the client must be using compatible software. One common solution is the three-tier client-server architecture, in which a middle tier, known as middleware, is placed between the server and the clients to handle the translations necessary for different client platforms. Middleware also works in the other direction, allowing clients easy access to an assortment of applications on heterogeneous servers. For example, middleware could allow a company’s sales force to access data from several different databases and to interact with customers who are using different types of computers.

·         Web Servers
A web server is a computer system that processes requests via HTTP, the basic network protocol used to distribute information on the World Wide Web. The term can refer to the entire system, or specifically to the software that accepts and supervises the HTTP requests.

Software
·         Software engineering
Software, instructions that tell a computer what to do. Software comprises the entire set of programs, procedures, and routines associated with the operation of a computer system. The term was coined to differentiate these instructions from hardware—i.e., the physical components of a computer system. A set of instructions that directs a computer’s hardware to perform a task is called a program, or software program.
The two main types of software are system software and application software. System software controls a computer’s internal functioning, chiefly through an operating system (q.v.), and also controls such peripherals as monitors, printers, and storage devices. Application software, by contrast, directs the computer to execute commands given by the user and may be said to include any program that processes data for a user. Application software thus includes word processors, spreadsheets, database management, inventory and payroll programs, and many other “applications.” A third software category is that of network software, which coordinates communication between the computers linked in a network.
Software is typically stored on an external long-term memory device, such as a hard drive or magnetic diskette. When the program is in use, the computer reads it from the storage device and temporarily places the instructions in random access memory (RAM). The process of storing and then performing the instructions is called “running,” or “executing,” a program. By contrast, software programs and procedures that are permanently stored in a computer’s memory using a read-only (ROM) technology are called firmware, or “hard software.”

·         Programming languages
Programming languages are the languages in which a programmer writes the instructions that the computer will ultimately execute. The earliest programming languages were assembly languages, not far removed from the binary-encoded instructions directly executed by the machine hardware.

·         Operating System (OS)
An operating system is a program that acts as an interface between the user and the computer hardware and controls the execution of all kinds of programs. Important functions of an operating System:
  1. ·         Memory Management
  2. ·         Processor Management
  3. ·         Device Management
  4. ·         File Management
  5. ·         Security
  6. ·         Control over system performance
  7. ·         Job accounting
  8. ·         Error detecting aids

Important activities that an Operating System performs −
Security − By means of password and similar other techniques, it prevents unauthorized access to programs and data.

Control over system performance − Recording delays between request for a service and response from the system.

Job accounting − Keeping track of time and resources used by various jobs and users.

Error detecting aids − Production of dumps, traces, error messages, and other debugging and error detecting aids.
Coordination between other software’s and users − Coordination and assignment of compilers, interpreters, assemblers and other software to the various users of the computer systems.


Computers are often considered one of the best invention in history, not just because of all the wonderful things they can do and the great improvements they have made in our lives but because of our relationship to them. Nowadays, it is very rare that people go even a few hours without checking the computer on their phone. Their computer is their buddy and it is literally attached to a hip.

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