A computer is a general purpose device which can be programmed to carry out a finite set of arithmetic or logical operations. Since a sequence of operations can be readily changed, the computer can solve more than one kind of problem. The essential point of a computer is to implement an idea, the terms of which are satisfied by Alan Turing’s Universal Turing machine.
Conventionally, a computer consists of at least one processing element and some form of memory. The processing element carries out arithmetic and logic operations, and a sequencing and control unit that can change the order of operations based on stored information. Peripheral devices allow information to be retrieved from an external source, and the result of operations saved.
A computer’s processing unit executes a series of instructions that make it read, manipulate and then store data. Conditional instructions change the sequence of instructions as a function of the current state of the machine or its environment.
In order to interact with such a machine, programmers and engineers developed the concept of a user interface in order to accept input from humans and return results for human consumption.
The first electronic digital computers were developed between 1940 and 1945 in the United Kingdom and United States. Originally, they were the size of a large room, consuming as much power as several hundred modern personal computers (PCs). In this era mechanical analog computers were used for military applications.
Modern computers based on integrated circuits are millions to billions of times more capable than the early machines, and occupy a fraction of the space.Simple computers are small enough to fit into mobile devices, and mobile computers can be powered by small batteries. Personal computers in their various forms are icons of the Information Age and are what most people think of as “computers”. However, the embedded computers found in many devices from mp3 players to fighter aircraft and from toys to industrial robots are the most numerous.
The Components of a Computer
A computer contain many electric,electronic,and mechanical components known as hardware.These components include input devices,output devices,and communication devices.Some common computer hardware components.
In computing, an input device is any peripheral (piece of computer hardware equipment) used to provide data and control signals to an information processing system such as a computer or other information appliance. Input and output devices make up the hardware interface between a computer and a scanner or 6DOF controller.
Many input devices can be classified according to:
- modality of input (e.g. mechanical motion, audio, visual, etc.)
- the input is discrete (e.g. key presses) or continuous (e.g. a mouse’s position, though digitized into a discrete quantity, is fast enough to be considered continuous)
- the number of degrees of freedom involved (e.g. two-dimensional traditional mice, or three-dimensional navigators designed for CAD applications)
Pointing devices, which are input devices used to specify a position in space, can further be classified according to:
- Whether the input is direct or indirect. With direct input, the input space coincides with the display space, i.e. pointing is done in the space where visual feedback or the pointer appears. Touchscreens and light pens involve direct input. Examples involving indirect input include the mouse and trackball.
- Whether the positional information is absolute (e.g. on a touch screen) or relative (e.g. with a mouse that can be lifted and repositioned).
Direct input is almost necessarily absolute, but indirect input may be either absolute or relative. For example, digitizing graphics tablets that do not have an embedded screen involve indirect input and sense absolute positions and are often run in an absolute input mode, but they may also be set up to simulate a relative input mode where the stylus or puck can be lifted and repositioned.
An output device is any piece of computer hardware equipment used to communicate the results of data processing carried out by an information processing system (such as a computer) which converts the electronically generated information into human-readable form.
A display device is an output device that visually conveys text, graphics, and video information. Information shown on a display device is called soft copy because the information exists electronically and is displayed for a temporary period of time. Display devices include CRT monitors, LCD monitors and displays, gas plasma monitors, and televisions.
Types of output
Some types of output are text, graphics, tactile, audio, and video. Text consists of characters (letters, numbers, punctuation marks, or any other symbol requiring one byte of computer storage space) that are used to create words, sentences, and paragraphs. Graphics are digital representations of nontext information such as drawings, charts, photographs, and animation (a series of still images in rapid sequence that gives the illusion of motion). Tactile output such as raised line drawings may be useful for some individuals who are blind. Audio is music, speech, or any other sound. Video consists of images played back at speeds to provide the appearance of full motion.
A digital image is a numeric representation of an image stored on a computer. They don’t have any physical size until they are displayed on a screen or printed on paper. Until that point, they are just a collection of numbers on the computer’s hard drive that describe the individual elements of a picture and how they are arranged. Some computers come with built-in graphics capability. Others need a device, called a graphics card or graphics adapter board, that has to be added. Unless a computer has graphics capability built into the motherboard, that translation takes place on the graphics card. Depending on whether the image resolution is fixed, it may be of vector or raster type. Without qualifications, the term “digital image” usually refers to raster images also called bitmap images. Raster images that are composed of pixels and is suited for photo-realistic images. Vector images which are composed of lines and co-ordinates rather than dots and is more suited to line art, graphs or fonts. To make a 3-D image, the graphics card first creates a wire frame out of straight lines. Then, it rasterizes the image (fills in the remaining pixels). It also adds lighting, texture and color.
Haptic technology, or haptics, is a tactile feedback technology which takes advantage of the sense of touch by applying forces, vibrations, or motions to the user. Several printers and wax jet printers have the capability of producing raised line drawings. There are also handheld devices that use an array of vibrating pins to present a tactile outline of the characters or text under the viewing window of the device.
Speech output systems can be used to read screen text to computer users. Special software programs called screen readers attempt to identify and interpret what is being displayed on the screen and speech synthesizers convert data to vocalized sounds or text.
These examples of output devices also include input/output devices. Printers and visual displays are the most common type of output device for interfacing to people, but voice is becoming increasingly available.
- Screen (Monitor)
- Voice output communication aid
- Automotive navigation system
- Braille embosser