المحاضرة الثانية
2- Input devices 2- Input devices Input devices allow you to input information Input devices allow you to input information 1- keyboard :- Contains the standard typewriter keys plus a number of specialized keys. The standard keys are used to enter words and numbers. Examples of specialized keys are so called function keys, labeled F1,F2 and so on
2- Input devices 2- Mouse :- A small hand – help device, which has the shape of a mouse. As it is moved, a rolling ball on the underside, transmits, which moves the cursor. The cursor is the symbol on the screen that shows where data may be entered next. It has two or three buttons to perform many action.it works when any of the buttons are pressed down.
Input devices Input devices 3- Scanners:- Scanners converts page contents text. Images, pictures, and graphics and so on into electronic signals.these signals can then be stored in a computer and manipulated.it can also be used to read bar codes.
Input devices Input devices 4- Bar Code Reader :- - Are the vertical zebra-striped marks you see on most manufactured retail products. - Bar codes are read by bar code readers, which are photoelectric scanners that translate the bar code symbols into digital forms. - Bar codes are read by bar code readers, which are photoelectric scanners that translate the bar code symbols into digital forms.
Other Input devices Microphone Microphone Digital camera Digital camera Video camera Video camera
Output devices Output devices allow you to output information from the computer Output devices allow you to output information from the computer Video display unit ( V D U) Video display unit ( V D U) Plotters Plotters Printers Printers
Output devices Video display unit ( V D U):- Video display unit ( V D U):- (monitors ) : displays the work being done by CPU, displays the results of processing, displays text, graphics, images,forms and so on. - Types of monitors : cathode ray - 2- panel display flat
Types of monitors :- 1- Cathode Ray Tube (CRT) :- Ti is a vacuum tube used as a display screen in a computer or video display terminal.this kind is found not only in the screens of desktop computers but also in television sets and in flight – information monitors in airports.
Types of monitors :- 2- A Flat – Panel Display :- Is a thin display screen that uses any of a number of technologies in order to reduce screen size and weight. The technologies include liquid crystal display (LCD), electro luminescent, and plasma displays. The screens in laptop computers must be flat panel display. - Characteristics of monitors : (a) colors (b) size (c) resolution (a) colors (b) size (c) resolution
Output devices Plotters :- Plotters :- A special printer, which uses pens to draw on the paper – and is under the control of the computer and the mapping software. It is used to draw maps, as well as complex technical drawing.
Output devices Printers :- Printers :- Are a device that converts computer output into printed images. Hard cope refers to printed output. Software copy refers to output that is in the form of sound or displayed on a computer screen. Type of Printers :- 1- daisy wheel 2- inkjet 3- laser Printers :-
Type of Printers Daisy wheel :- characters are raised on a wheel, which strikes the ribbon placed between them, and paper. It is an impact, which is both slow and noisy. It produces carbon copies. Daisy wheel :- characters are raised on a wheel, which strikes the ribbon placed between them, and paper. It is an impact, which is both slow and noisy. It produces carbon copies.
Type of Printers 2- Inkjet :- Spray one or more colors of small droplets of ink at high speed onto paper. It running cost is high. Carbon copies can't be produced.it is color printer with either a one color cartridge or a multiple color cartridge. It is quiet but slower than the laser printers.
Type of Printers 3- Laser Printers :- Use a laser – beam source to create dot – like images on a drum. These images are then treated with magnetically charged ink – like toner and transferred from drum to paper.