Coputer input and output parts details
THE CENTRAL PROCESSING UNIT
Processor:- The heart of any computer system. It consists of ALU, control elements and small memory units called registers.
ALU:- All calculations and all comparisons take place in this unit.
Control Unit:- This interprets any instruction it receives from memory and directs the sequence of events Necessary to execute the instruction. CU uses a system clock which synchronizes all tasks by sending out electrical pulses.
INPUT DEVICES
Input devices are used to feed data and instructions to the computer system.
Input devices provide the interface between the outside world and the computer system for this purpose. An input device is a peripheral which accepts data and sends it to the central processing unit.
Ex. of input devices 1. The keyboard 2. Alight pen 3. An Electronic digital weighing scale interface d to a computer 4. A document reader 5. A mouse. INPUT FROM KEY BOARD
The usual keys supplied are
1. The alphabet 9 3. Other text c
2. The digits 0-haracters
nd other control characters 5. Keys wh
4. Cursoraich change the function of other keys
DOCUMENT READERS
MR, OCR and MICR
OA document reader is a device which read data straight from a form.
Ex; 1. Optical Mark Recognition(OMR) 3. Magnetic Ink Character Recognitio
2. Optical Character Recognition(OCR)n(MICR)
OPTICAL MARK RECOGNITION. (OMR)
MR is a system of reading lines or marks which have been made in exactly the right positions on a card or document.
O
APPLICATIONS OF OMR
The documents to be read have empty boxes to take the marks. These have been preprinted on to the documents together with information telling the user what to do. The person preparing the data makes pencil or ink marks in the appropriate boxes.
The data to be input has to be simple because the user can only make marks and cannot write any information. There has to be large number of documents to justify designing and printing them. Ex: marking multiple choice question papers. OPTICAL CHARACTER RECOGNITION (OCR)
n optical character reader can recognize characters from their shape. As with OMR light is reflected from the paper and form the ink. In OCR however the reader has to workout what the characters are.
AScanners were originally design to scan pictures but they can also be used to read text.
MOUSE
A mouse is an input device designed to fit snugly under a hand while it is moved about over a table. Moving the mouse produce s movements of a cursor or a pointer on the screen.
The mouse is also provided with one, two or three buttons. These are pressed to produce action when the user has moved the cursor to the right place. USES OF MOUSE:
1. To select options from a menu or from a set of icons.
2. To position the cursor when editing text or using a design packages.
3. To select an object in a drawing or a piece of text to be copied, moved or deleted.
OUT PUT DEVICES
here are several ways to produce output:
T1. Text output. 2. Graphics output.
TEXT OUTPUT
Is simply alphanumeric characters that makeup our language. Text output appearance ranges from type writer to typeset quality.
GRAPHIC OUTPUT
Includes line drawings, maps, presentations business graphics.
SOUND OUTPUT
Ranges from the message beeps produced by the computer system to the human voice to music and other forms of sound.
VIDEO OUTPUT
Photographs (still images) or moving images such as television and video taped material
Again we have 2 principle kind of output are: 1. Hard copy. 2. Soft copy. PRINTER isual records called hard copy. The basic criteria for evaluating printers include: 1. Quality of the printed output. 2. Speed at which printed pages are produced. 3.
A printer is read only device, driven directly by a computer and provide permanentv Sound level during printing. 4. Cost of printing media. 5. Conservation of paper.
BASIC CLARIFICATION OF PRINTERS
. Character printers. - Prints one character at a time.
12. Line printers – Prints one line at a time.
BASIC METHODS OF PRODUCING PRINTOUTS
IMPACT PRINTERS:
Form characters or images by striking mechanism Such as print hammer or wheel against an inked ribbon leaving an image on paper.
Ex Low speed impact printers (Daisy wheel print head, Dot matrix printer head) NON-IMPACT PRINTERS
Form characters or images without making direct physical
contact between printing mechanism and papers. DOT MATRIX PRINTER
his mechanism enable the print control up to the dot level on the paper, can be used to produce both text and graphics. Fast but noisy wear out ribbons very quickly.
T
LASER PRINTER
. Excellent print quality and font selection.
12. Fast printing and high quality graphics with color, high resolution
3. Medium level noise but high cost. e maintenance and the high cost of toner cartridges.
4. Primary disadvantages are expensivINK-JET PRINTERS
nk jet printers’ transfers characters and images to the paper by spraying a fine jet of ink.
IOffers nearly the quality of laser printing but not the speed. Low cost alternative for high quality printing.
MONITOR
rovide soft copy out put. Comes in either monochrome or color.
P1. A monochrome display a single color against a different color background
2. Color display can show variety of colors. Resolution- Describe the degree of details in a video display.
The higher the resolution the characters and images are sharper and crisper as fill image.
PLOTTERSIt is a specialized output device designed to produce high quality graphics in a variety of colors. Those are especially useful for creating maps and architectural drawings, although they may also produce less complicated charts and graphics.
TYPE OF PLOTTERS
1. Pen plotter
2. Electrostatic plotter.
3. Thermal plotter.