Preparing a program

Preparing a program 

Begins with a complete description of the job that the computer is to perform. This job description is obtained from the person for whom the program is being prepared, such as a business man ager or an engineer. It explains what input data are needed, what computing must be done, and what the output should be. Computer programmers use the description to prepare diagrams and other pictorial aids that represent the steps needed to complete the task. The programmers may produce a diagram called a system flow chart that shows how all the major parts of the job fit together systematically . After a computer program is written, it is tested on the computer for mistakes. Computer refer to mistakes in programs as "bugs" and the testing of programs as "debugging".

    A program generally is entered into a computer in what is known as an interactive environment. In such an environment, the programmer enters part of the program on a computer terminal. The computer's operating system responds immediately, telling the programmer how the computer will interpret each instruction. The programmer then can analyze each response. Programs that result from this interaction between the programmer and the computer generally are stored on some type of file storage device until needed.

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Programming a computer

Programming a computer 

Programming involves the preparation and writing of detailed instructions for a computer. These instructions tell the computer exactly what data to use and what sequence of operations to perform with the data. Without programs, a computer could not solve problems or deliver any other desired result.  

    Some people prepare their own computer programs. But in many cases, computer scientists and other computer specialist called programmers write instructions for computers. They use programming languages that consist of letter, words and symbols, as well as rules for combing those elements. 

     A computer cannot work directly with a program written in a programming language. The instructions must be translated into a machine language composed of binary digits. These digits represent operation codes, memory addresses, and various symbols such as plus and minus signs. Machine language is also known as low level language. Special programs called compilers and assemblers translate programming languages into machine Language. Another special type of program called an operating system contains instructions for the operation of a computer. It controls the input and output devices, and it reads and responds to user commands. It also places programs and data into the memory and makes sure that the processor executes the right programs. Thus, the operating system combines the many separate parts of a computer into a single useful system.

     Compilers, assemblers and operating systems may be viewed as "smart (Intelligent) programs" because they enable a computer to understand complicated instructions. The user communicates with the smart program  and the smart program communicates with the computer. A computer combined with a smart program acts like a different, smarter computer. This combination is called virtual machine.http://m.wikihow.com/Start-Learning-Computer-Programming

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Mainframe computer

Mainframes are fast computers with large memories and file storage systems. These powerful computers solve very complicated problems and manage huge quantities of information. Most mainframes are housed in several large cabinets. Some mainframes do a single job, such as copying and storing the information generated by a laboratory experiment. Others perform many different tasks. Minicomputers and superminis have many of the capabilities of mainframes, but they are smaller and less expensive. 

    On a large mainframe, hundreds of people maybe logged on running programs at one time. The use of a single powerful computer by many users at once is called time -sharing. However, the computer actually switches rapidly from program to program, doing a bit of work on me and then hurrying on to work on another.

    The fastest mainframes are called supercomputers. Supercomputers solve numerical problems as quickly as possible based on existing technology. They are used to model weather systems, to design cars and aircraft in many other ways. Likewise supercomputers are rare, because they are extremely expensive. Supercomputer users mostly scientists and engineers at large scientific installations sometimes run programs by means of long distance computer networks. 

    In recent years, mainframes known as parallel computers have provided great increases in speed over other computers. Most computers have a single processor. Where as a parallel computer has many processors that all operate at once. Each processor can work on a separate piece of a program. As a result, the program can be run much more quickly than on a computer with only one processor. The fastest supercomputers in the world are parallel computers. Like wise parallel computers may even serve as especially fast workstations.

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Communications satellite

Communication satellite is a spacecraft that orbit the earth and has equipment for relaying radio, telegraph and television signals. Stations on the ground,called earth stations, transmit signals to the satellite, which then broadcasts the signals to other earth stations.

   Communications satellites allow telephone conservations, telegraph messages and radio and TV programs to travel from one part of a country to another or even across oceans. They also can handle huge amounts of data. For example, all the files and records from a computer in the United States can be sent to a computer in Europe via satellites stationed over the Atlantic Ocean also can handle about 30,000 phone calls at one time. Without satellites, extensive networks of wires or cables would be needed to achieve lite broadcasts can reach a large number of people at the same time.

          Most communications satellites are built, launched and operated by large companies or Government agencies. Some communications satellites are used by only one country for transmissions to and from areas by only one country for transmission to and from areas within such domestic satellites. As many as 50 countries now operate satellite systems. The Aussat satellite system in Australia combines telecommunications with a direct television broadcasting system. India and China also have been able to install nationwide communications systems using satellites.

         Some communications satellites are shared by several countries. Many of these satellites function as a network. The satellites in such communications satellites systems are designed to relay signals among themselves as well as to the ground. In this way, signals can be transmitted around the world. For example, more than 140 countries used the service of the INTELSAT system, a network of communications satellites that reach more than 600 earth stations worldwide. Other communications satellite systems include Eutelsat, which serves a number of European nations, and Arabsat, used by Arab league. 

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Personal computers

Computer, Personal,  is a desktop or handheld computer designed for general purpose use. Personal computer design are used by individuals, families, schools and companies for such purposes as keeping records, Writting reports, learning a new subject, playing games, programming or even running household appliances.
      All computers store and handle information. Many large businesses use large, expensive computers that must be shared by a number of people to be economical. Personal computers, because they are equipped with one or more microprocessors. Microprocessors, which were introduced in 1971, are miniature electronic devices that can handle many of the same tasks as a large computer, though more slowly and with smaller amounts of information. The development of microprocessors led to a reduction in the cost of computers and thus made it possible for computers to be purchased by individuals, school and small companies.

USES OF PERSONAL COMPUTER
Like other computers, personal computers can be instructed to perform a variety of individual functions. A set of instructions that tells a computer what to do is called a program. Today, more than 10,000 application programs are available for use on personal computers. they include such popular programs as word processing programs, spreadsheet programs, database programs and communication programs.
 Word processing programs are use to type, correct, rearrange, or delete text in letters, memos, reports and school assignments. Spread sheet programs enable individuals to prepare tables easily. The users of such programs will calculate and fill in the rest of the table. When the user change according to the rules established by that user. Spread sheets may be used for preparing budgets and financial plans, balancing a cheque book or keeping track of. Personal investments.
     Database programs allow a computer to store large amounts of data (information) in a systematic way. Such data might include the name, address, telephone number, salary and starting date of every employee in a company. The computer could then be asked to produce a list of  all employees who receive a certain salary.
   Communication programs connect a personal computer to other computer. People can thereby exchange information with one another via their personal computers. In addition, communication programs enable people to link their personal computers with databanks. Databanks are huge collection of information stored in large centralized computers. News, financial and travel information and other data of interest to many users can be obtained from a databank.
 Other programs include recreational and educational programs for playing games, composing and hearing music and learning a variety of subjects. Programs have also been written that turn household appliances on and off. Some people develop their own programs to meet need not covered by commercially prepared programs. Others buy personal computers mainly to learn about computers and how to program them.
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Importance of the computer

Computers are tremendously important in a variety of ways. For example, they simplify many difficult or time consuming tasks to an extraordinary degree. They provide businesses, Government, individuals and institutions with an efficient way to manage large amounts of information. Computers also help people understand things better by allowing them to make models and test theories.

   The value of computers lies in their ability to perform certain basic tasks include (1.) solving numerical problems (2.) Storing and retrieving information and (3.) creating and displaying documents and pictures.

SOLVING NUMERICAL PROBLEMS. One of the most important and most difficult jobs performed by computers is the solution of complicated problems involving numbers. Computers can solve such problems amazingly quickly. In many cases, the solutions show how certain things work, behave, or happen.

Storing and retrieving information. A computer can search a huge database quickly to find a specific piece of information. In addition, the information can be changed easily and quickly often in less than a second. 

In economics and finance, computers solve equations to make predictions about money. Many of the equations that economists and business people use to make long range predictions are extremely complicated. But some of the most widely used of all computer programs rely on fairly simple equations. Such programs rely on fairly simple equations. Such programs help people and businesses work out their taxes, create budgets and calculate the value of their investments.

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Computerized tomography

Computerized tomography (CT) is an x-Ray system used to produce images of various parts of the body, such as the head, heart and abdomen. Doctors use CT images to help diagnose and treat diseases. The technique is also called computer tomography or computerized axial tomography (CAT).
      To produce a CT image, the patient lies on a table that passes through a circular scanning machine called a gantry. The table is positioned so that the organ to be scanned lies in the centre of the gantry. A tube on the gantry beams X Rays through the patient's body and into special detectors that analyse the image produced. The gantry rotates around the patient to obtain many images from different angles. A computer then processes the information from the detectors to produce a cross sectional image on a video screen. By moving the table in the gantry, doctors can obtain many scans of the same organ or even the entire body.
   Sometimes an iodine solution, called a contrast agent, is injected into the body to make certain organs show up clearly in the CT scan. For scans of the abdomen and pelvis, the patient drinks a barium mixture (which is opaque to X Rays) to outline the inner surfaces of the stomach and bowel.
     Doctors use CT scans to diagnose many conditions, such as tumours, infections, blood clots and broken bones. CT also assists in treating some diseases that might otherwise require surgery. For example, doctors can use a CT scan to guide catheters ( small tubes) to an abscess in the body and drain pus from infected area.

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computer graphics

What is Computer Graphics are images created by a computer. These images include diagrams, cartoon animations, and even highly realistic pictures. The process by which computers draw , colour,   Shade and manipulate images is also known as computer graphics. Computer graphics enable us to gather , display and understand information quickly and effectively. Computer graphics can even produce images of objects and processes that we have no other way of seeing , such as inside of a molecule or the operation of a black hole .
      Computer graphics have numerous uses in a wide variety of fields. Business follow sales from charts and graphs made by computers. Computer graphics help Engineers create and test designs for such products as cars and aircraft. Through computer graphics , architect can view building designs drawn in three dimensions from any angle . Scientists use computer graphics to design new drug molecules, track weather systems, and test theories that describe how galaxies develop. Doctors use computer images of the inside of the body to locate tumours and other disorders and plan treatment (see COMPUTERIZED TOMOGRAPHY (CT) . Computer graphics are also used in art , in the production of cartoons and special effects in films and in video games . Computer graphics are created on a computer display screen , which resembles a television screen . The screen consist of thousands of tiny dots called pictures.
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