Computer World Home

Computers are like air conditioners, they stop working properly if you open Windows.

  Man is still the most extraordinary computer of all. (John F. Kennedy)

» History of Computers

» Categorization

» Types of Computers

» How Computers Work

» Operating System (OS)

» Computer Memory (RAM) + Conversion Table

» Input and Output Devices

» Central Processing Unit (CPU)

» Programming Languages

» Networks

» Future Developments

» First Known Virus
 

Computer is a device that computes, especially a programmable electronic machine that performs high-speed mathematical or logical operations or that assembles, stores, correlates, or otherwise processes information., under the control of instructions called a program. Programs are usually stored within the computer to be retrieved and activated, with results stored or sent to output devices such as video screens. People use computers in business, in homes, in automobiles, in education, in scientific research, for entertainment, and for military functions.

History of Computers
In 1623 German scientist Wilhelm Schikard invented a machine that could add, multiply and divide. French philosopher, mathematician, and physicist Blaise Pascal invented a machine in 1642 that added and subtracted, automatically carrying and borrowing digits from column to column. Seventeenth-century German mathematician Gottfried Leibniz designed a special gearing system to enable multiplication on Pascal's machine.

In the early 19th century French inventor Joseph-Marie Jacquard devised a loom that used punched cards to program patterns of woven fabrics. The Difference Engine, designed in the early 1820s by British mathematician and scientist Charles Babbage, was intended to solve mathematical problems. Babbage also made plans for the Analytical Engine, considered to be the forerunner of the modern computer.

Herman Hollerith, an American inventor, combined the use of punched cards with devices that created and electronically read the cards. Hollerith's tabulator was used for the 1890 United States census. Hollerith's Tabulating Machine Company eventually merged with other companies in 1924 to become International Business Machines Corporation (IBM).

In the 1930s American mathematician Howard Aiken developed the Mark I electronic calculating machine, which was built by IBM. Hungarian-American mathematician John von Neumann developed the first electronic computer to use a program stored entirely within its memory. John Mauchley, an American physicist, and J. Presper Eckert, an American engineer, in 1945 built the first successful, general digital computer.

In 1948 American physicists Walter Houser Brattain, John Bardeen, and William Bradford Shockley developed the transistor. In the late 1960s integrated circuits, electrical components arranged on a single chip of silicon, replaced individual transistors. In the 1970s came the development of the microprocessor. Modern microprocessors contain as many as 10 million transistors.

Manufacturers used integrated circuit technology to build smaller and cheaper personal computers. Refinements of the PC included video displays, better storage devices, stronger CPUs, and graphical user interfaces with icons and windows representing programs.

Categorization

Class:- Computers can be classified as supercomputers, mainframes, super minicomputers, minicomputers, workstations, or microcomputers. All other things (for example, the age of the machine) being equal, such a categorization provides some indication of the computer’s speed, size, cost, and abilities.

Generation:- First-generation computers of historic significance, such as UNIVAC, introduced in the early 1950s, were based on vacuum tubes. Second-generation computers, appearing in the early 1960s, were those in which transistors replaced vacuum tubes. Third-generation computers, dating from the 1960s, were those in which integrated circuits replaced transistors. Fourth-generation computers, appearing in the mid-1970s, are those, such as microcomputers, in which large-scale integration (LSI) enabled thousands of circuits to be incorporated on one chip. Fifth-generation computers are expected to combine very-large-scale integration (VLSI) with sophisticated approaches to computing, including artificial intelligence and true distributed processing.

Mode of processing:- Computers are either analog or digital. Analog computers, generally used in scientific pursuits, represent values by continuously variable signals that can have any of an infinite number of values within a limited range at any particular time. Digital computers, the type most people think of as computers, represent values by discrete signals-the bits representing the binary digits 0 and 1.

Types of Computers
Digital computers manipulate numbers that represent switches turned on or off by electrical current. Analog computers use numerical values with a continuous range, including fractions. Analog computer systems were the first type produced. Most modern computers are digital.

Tiny computers in other devices are typically preprogrammed for a specific task, such as tuning to a particular television frequency or keeping accurate time. Programmable computers vary enormously. The smallest of these computers can be held in one hand and are called personal digital assistants (PDAs). Laptop computers and personal computers (PCs) have large amounts of internal memory to store hundreds of programs and documents. Workstations are similar to personal computers but have greater memory and more extensive abilities. Mainframe computers have more memory, speed, and capabilities than workstations and are usually shared by multiple users. The most powerful mainframe computers, called supercomputers, process hugely complex calculations, such as those used to create weather predictions.

How Computers Work see a graph
Physical computer equipment, called hardware, includes the memory that stores data and programs; the central processing unit (CPU) that carries out instructions; the input devices that allow the user to communicate with the computer; and the output devices that present information to the user. Computer programs are called software.

The Operating System (OS)
A program called the operating system makes the computer work. It stores and manages data and controls the sequence of the software and hardware actions. When the user requests that a program run, the operating system loads the program in the computer's memory and runs the program.

Computer Memory
Data are stored in a computer as binary digits, or bits in harddisk. Bit is the smallest unit of information handled by a computer. One bit expresses a 1 or a 0 in a binary numeral, or a true or false logical condition. A group of 8 bits makes up a byte, which can represent many types of information, such as a letter of the alphabet, a decimal digit, or other character. Bit is also called binary digit. Below is the comparison table of all available conversions:

The physical memory of a computer is either random access memory (RAM), which can be read or changed by the user or computer, or read-only memory (ROM), which can be read but not altered. Computer chips hold memory, as do floppy disks, hard disks, and CD-ROMs (compact discs).

Input and Output Devices
Input devices include; keyboard, mouse, joystick, optical scanner, light pen, touch panel, and microphone. Output devices include the cathode-ray tube, liquid crystal display, printer, overhead projector, videocassette recorder (VCR), and speaker.

The Central Processing Unit (CPU)
The CPU is a microprocessor chip that translates commands and runs programs. The CPU's control unit coordinates and times the CPU's functions, and it retrieves instructions from memory. The CPU executes instructions and stores results or sends them to memory locations.

Programming Languages
Programming languages contain the commands that create software. A language that a computer's hardware understands runs faster. Languages that use words are easier but slower. Instructions for the CPU are in simple numerical machine code. Because this code is not understood easily by humans, computer instructions usually are not written in machine code.

Assembly language uses commands that are easier for programmers to understand. Once an assembly language program is written, it is converted to a machine language program. High-level languages are easier to use than machine and assembly languages because their commands resemble natural human language. A compiler program turns a high-level program into a machine language.

Networks
Computers can communicate with other computers through a network to exchange data and share software and hardware resources. A local area network (LAN) consists of several PCs or workstations connected to a special computer called the server. The server stores and manages programs and data. Mainframe computers and supercomputers commonly are networked. They may be connected to PCs, workstations, or "dumb" terminals used only to enter data into, or receive output from, the central computer.

Wide area networks (WANs) span large areas. Computers can connect to these networks to use facilities in another city or country. The largest WAN is the Internet. The World Wide Web is a system of information accessed through the Internet.

Future Developments
The number of transistors and the computational speed of microprocessors currently doubles approximately every 18 months. Components continue to shrink in size and are becoming faster, cheaper, and more versatile. With their increasing power and versatility, computers simplify day-to-day life. Unfortunately, as computer use becomes more widespread, so do the opportunities for misuse (see Computer Security). New ethical issues also have arisen, such as how to regulate material on the Internet and the World Wide Web.

Computers will become more advanced and they will also become easier to use. Reliable speech recognition will make the operation of a computer easier. Communications between computer users and networks will benefit from new technologies such as broadband communication systems that can carry significantly more data and carry it faster.

First Known Virus
The first known virus was created to run on Apple II machines. The virus was a program called "Elk Cloner" and it was distributed with a game on a floppy disk. After the 49th execution of the game, the virus would display a poem message and infect the computer. In 1986 the first PC virus called "(c)Brain" was created by two brothers from Pakistan in order to prevent pirated copies of software they invented. The virus changed the label of 360 KB floppy disks to "(c)Brain,".