Computer World ++
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)
» Operating System (OS)
» Computer Memory (RAM) + Conversion Table
» Central Processing Unit (CPU)
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.
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.
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.
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.
Data are stored in a computer as binary digits, or bits in hard disk. 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 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 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 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.
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.
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.
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,".