Components
of the Computer and Their Use
A computer consists of five primary hardware components: input devices, the central processing unit (CPU), memory, output devices, and storage devices. These components work together with software to perform calculations, organize data, and communicate with other computers.
Different types of input devices transmit different types of data or transmit data in different ways. A keyboard is used to transmit alpha/numeric data by typing. In addition to the standard keys in the typing area, an enhanced keyboard contains:
Function keys that can be programmed to perform specific tasks
Status lights that indicate modes that can be turned on and off
by toggle keys (e.g., caps lock and num lock)
A numeric keypad that allows for rapid entry of numbers
Arrow keys and other cursor-control keys (e.g., home, end,
page up, and page down) that control the on-screen movement of the insertion
point
Special keys such as esc, shift, ctrl, and alt that have varying functions depending on the software
The mouse, like a trackball or joystick, is called a pointing device because it controls the movement of a pointer, or mouse pointer, on the computer screen. The first mouse was a one-button, rectangle shaped device invented by Doug Engelbart in 1964. A mouse is very easy to use. It requires empty desk space, however, and forces the user to remove a hand from the keyboard to give a command.
Different CPUs function at different speeds. The rate at which
computer operations take place is measured in gig hertz (GHz), or billions of
electronic pulses per second. This rate varies among computers and should be a
consideration when purchasing a personal computer. Computers have two basic
types of memory. RAM (random access memory) is volatile, meaning that its
contents are lost when the computer is turned off. ROM (read-only memory) is non-volatile
because it retains its contents even when the power is turned off. ROM stores
information that does not change, such as the instructions and data used to
start the computer when it is first turned on.
Like input devices, different types of output devices convey different types of information or convey information in different ways. Printer output sometimes is called hard copy because of its physical, touchable character. Monitor output, on the other hand, is called soft copy because it has only an electronic, intangible existence.
Non-impact printers represent the fastest growing segment of the printer market. The drops of ink that form an ink-jet printer character are similar to the dots that form a dot matrix character figure, but there are many more of them. Good quality paper must be used with ink-jet printers so that the ink does not bleed. The speed quoted for impact printers often is measured in characters per second (cps). Like ink-jet printers, laser printer speed is measured in pages per minute (ppm). Although they are fast, all printers are much slower than computers. Because of this, most printers have a buffer that temporarily stores a few pages, allowing the computer to dump output into the buffer and continue processing. The most widely used PC monitors are 14- or 17-inch (measured from one corner to the diagonally opposite corner). With the growing popularity of portable computers, the clarity of LCD displays continues to improve. The quality of a monitor's display depends largely on three factors:
·
Resolution - the number of pixels displayed
·
Dot
pitch - the distance
between pixels
·
Refresh
rate - the speed with
which images are redrawn on the screen
·
Storage
devices are different from memory. Memory, sometimes called primary storage, is
fast, short-term, volatile, and relatively expensive. Storage devices, on the
other hand, are slower, long-term, non-volatile, and less expensive.
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