Microsoft Word 2007.pdf

Input/Output Methods 

There are three basic methods by which data can be read (or input) from or written (or output) to a peripheral device and RAM. These methods are referred to as: programmed I/O, interrupt I/O, and direct memory access. In programmed I/O, the MPU directly controls all data transfers and other I/O operations. 

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This is accomplished with input or output instructions. When an input operation is desired, the MPU issues an input command and awaits the arrival of the data at the bus. From the bus the data are moved to memory. Similarly for an output operation, the MPU transmits the data to the bus and issues a command to the output device through the appropriate interface. Once data transfer is initiated, the MPU should wait for its completion and the bus to be freed before beginning a new transfer. This method is commonly used in personal computers. In the interrupt I/O method, the MPU does not wait for the input/output devices to complete their tasks. The control of the operation is given to a channel. The channel signals the MPU when the operation has been completed. This is accomplished by means of an interrupt. Upon completion of the execution of the current instruction, the MPU may then initiate another I/O operation. Direct memory address method is the fastest of the three methods. It requires a multibus architecture and allows the MPU to be bypassed completely. A direct memory access controller is connected between RAM and an input or output device. This method is the most expensive of the all and therefore is not used except with very high-speed input/output devices. 

Telecommunications Between Microcomputers 

Most microcomputers also support the transfer of data through telephone line. This is facilitated by means of an add-on device known as a modem. In telecommunications, one computer or terminal issues a command, or some form of output. This digital output from the computer, is modulated, or converted to an analog signal, by a modem interfaced to the sending computer. The signal is then carried over the telephone line and received at another modem some distance away. This second modem then demodulates, or converts the analog signal back to a computer-compatible digital signal. The name modem performs the functions of modulation and demodulation. Thus, with the aid of a modem and a serial interface to a microcomputer, communication can take place over long distances. The speed with which these communications take place is dependent on the modem employed.

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Computer Sikun

Lesson 1: Introduction and Basic Organization 

1.1 Learning Objectives 
On completion of this lesson you will be able to
i) grasp the introductory concepts of a computer and its working principle
ii) understand the basic elements of a computer system.

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1.2 What is a Computer? 

A computer is an electronic machine that stores, retrieves, and manipulates or processes data. It cannot think or reason; it can only carry out instructions given to it. A set of instructions that directs its actions is called a program. Different programs are used to solve different problems. Ability to accept, store, and execute various sets of instructions (or programs) makes the computer the invaluable, allpurpose business tool. The first step of solving a problem by a computer is to develop a suitable computer program and then store in its memory. The computer then carries out the instructions in the program. The instructions of a program generally direct the computer to perform three basic functions over and over again; these functions are input, processing, and output. Collectively, these functions constitute the data processing cycle. 

Input: input devices are connected to feed the computer facts or data to be processed.

Processing: the control and storing of data, numerical comparisons, and arithmetic operations are performed on the input data to produce the desired results.

Output: the computer feeds the processed data or information, to the output devices.

i) The computer reads a program and stores it in the memory. The computer executes program instructions to:

ii) Input data from the disk, the keyboard, or other storage media,

iii) process the data and

iv) Output results to the display screen, disk or other media.

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HTML E-Book

2.5. Optical Mark Reader

Optical mark readers (OMR) optically read marks on carefully printed forms. Optical mark forms are relatively expensive, as they must be printed with exact tolerances so that the marks will up under the optical sensing devices when read. The most popular use of such devices is optical character readers for scoring examinations in educational institutions.

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2.6. Optical Character Recognizer

Optical character recognition (OCR) devices can convert data from source documents to a machine-recognizable form. OCR Current applications of optical scanning include billing, insurance premium notices, and charge sales invoices. At present, on OCR device can reliably read and interpret script or handwriting.

However, some can read handwriting provided that certain general guidelines are observed when the data are written. Generally, optical character readers are limited with respect to hand-written characters and can only read handwritten digits and some symbols. Many OCR devices are available for the reading of typed characters, including digits, letters and some special characters. Not all printed characters can be read reliably on OCR readers. Generally, each reader is capable of reading only selected character styles.

Even if the character style and spacing are acceptable, errors can result from reading a character that is not written perfectly. To reduce such errors, OCR devices generally compare the pattern read with the patterns to all acceptable character. The read character is assumed to be the character whose stored pattern most closely matches the read pattern.

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Setup Guide

Lesson 3 : Monitor

3.1. Learning Objectives
On completion of this lesson you will be able to describe:
 Working principle of display monitors
 Different types of monitor
 Using television as a monitor.

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3.2. Working Principle

It is the most commonly used display device. The monitor utilizes a cathode ray tube (CRT). CRT monitors generally produce images by the raster-scan method. In this method, an electron beam varying in intensity is moved back and forth horizontally across the face of the monitor. As the beam is directed to each spot on the phosphor-coated screen, it illuminates the spot in proportion to the voltage applied to the beam. Each spot represents a picture element or pixel. When the electron beam has scanned the entire screens and illuminated each pixel. One can see a complete image. The image that can be seen is the one traced on the retinas of eyes by the light beam. However, this image will fade unless it is refreshed. Thus, the electron beam must scan the screen very rapidly (a minimum of 60 times per second), so that the intensity of the image remains approximately the same and the screen docs not appear to flicker.

The number of pixels that make up the screen determines the screen resolution of a particular monitor. Monitors are currently available with 64,000 to more than 2 million pixels per screen. The greater the resolution of a monitor the greater the storage demand on the computer. This is because the image must he stored in memory before it can he displayed. Two techniques used to store computer images are bit-mapped and character-addressable. In a bit-mapped display, each pixel is uniquely addressable.

Information must be stored for each pixel on the screen. This technique needs quite a large computer memory and provides the most detailed display. For graphical applications, such as CAD/CAM, this detail is essential. However, for applications such as word processing, addressable display is appropriate. In a character addressable display, the screen is divided into character positions. Only the characters to be displayed are stored in memory. As each character is retrieved from memory, it is converted into a pattern of dots or pixels by a special character generator module.

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Information and Communication Technology.pdf

Lesson 4 : Printer

4.1. Learning Objectives
On completion of this lesson you will be able to describe:
 Different types of printers
 Working principle of different types of printers.

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4.2. Introduction

The printer is the most common output device. It produces permanent visual record of the data output from a computer. It is capable of producing business reports and documents currently available. Printers are capable of printing from 150 to over 20,000 lines per minute, with each line having up to 150 characters. Thus, a maximum printing speeds of approximately 50,000 characters per second is possible.

Printers print on plain paper or on specially prepared single-or multiple copy forms, such as invoices, stationery, labels, checks, bills and other special-purpose forms used in business and industry. They can print both text and graphics in black and white or in color. Printers can be subdivided into two broad categories, impact and non-impact.

4.3. Impact Printers

In impact printers, printing occurs as a result of a hammer striking a character form and the character form in turn striking an inked ribbon, causing the ribbon to press an image of the character on paper. Character printer devices print one character at a time at speeds of about 10 to 500 characters per second. Thc fastest of these printers is the wire or dot matrix printer. It prints characters made up of a pattern of dots formed by the ends of small wires. By extending certain wires beyond the others, a dot pattern can he created that gives the appearance of numbers, letters or special characters.

These extended wires are pressed against an inked ribbon to print the characters on the paper. Some slower and less expensive matrix printers print a character as a series of columns each one dot wide. It can be used to print special character shapes that can be used with graphics.

For a typewriter-quality output, a special dot matrix or daisy metal print element, similar in appearance to the arrangement of petals on a daisy flower. This element is rotated until the correct character is in position, and then pressed against an inked ribbon. The process as repeated for each character to be printed on a line. Typical for such printers range from 25 to 100 characters per second.

Impact character printers are the common output devices used with personal and small business microcomputer systems. They are significantly cheaper than the line printers.

Impact line printers, capable of printing a whole line at a time, employ print wheels or a moving chain or drum. The print-wheel printer consists of print wheels, each containing a full complement of digits and alphabetic characters in addition to a set of special characters. For printing, all print wheels rate positioned to represent the data to be printed on one line. They then impact simultaneously at a speed of about 150 lines per minute.

Impact line printers and the chain and drum printers are commonly used. As the print chain or drum revives, each character is printed as it comes into position. Up to 150 characters per line can he printed at speeds of up to 2,500 lines per minute. Impact line printers are used almost exclusively to support larger computer systems.

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Auto Cad Book.pdf

Lesson 8 : Hard Disk Drive Interface 

8.1. Learning Objectives On completion of this lesson you will be able to describe:
 What is hard disk drive interface
 Different types of hard disk drive interface.

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8.2. Introduction to Drive Interface 

Drive interface is the world wide predefined standard by which a controller can talk to its drive. This standard defines the cable and connectors between the controller and the hard disk and the language by which they talk together. We can get controllers from different industries and also hard disk drives from different industries. But there is no problem because of the interface. For example, if we connect the controller of one industry having IDE interface with a hard disk drive of another industry having IDE interface, they can work together because the interface (i.e., the language) between them is the same. Different drive interfaces are available. We have discussed here some common interfaces like ST506, ESDI, SCSI and IDE. 

8.3. ST506 

Here ‘ST’ stands for ‘Shugart Technologies’ because this interface is first defined by this industry. It has the following characteristics: 

 A 20 wire cable for data signals 

 Another 30-wire cable for control signals. 

 5 Mbps (Meg bit per second) data transmission rate 

 Supports up to 16 head disks 

 Short cable length 

 Prone to noise 

 Slower controlling method than other interfaces 

 Can not send drive information (how many platters, tracks etc.) to the controller. 

 Used in old models of computers. 

8.4. ESDI 

It is an advanced design of ST506. Some problems of ST506 interface are removed in this modified design. It has the following characteristics:

 Cabling same as ST506 (20-wires data and 34-wires control).

 Supports up to 256 head

 24 Mbps data transfer rate.

 Allows longer cables

 More noise free

 Can send drive information (how many platters, tracks etc.) to the controller.

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Computer and Information Technology.

Lesson 4 : Monitor Program 

4.1. Learning Objectives 
On completion of this lesson you will be able to describe:
 Monitor program or BIOS  Different types of BIOS
 Function of BIOS
 How the BIOS works

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4.2. Monitor Program in Microcomputer 

Monitor program is the program that is used to control the basic functions of different devices. In microcomputers the monitor program is known as BIOS. BIOS is the acronym for ‘Basic Input / Output System' in the PC, a set of instructions, stored in read-only memory (ROM), that let your computer's hardware and operating system communicate with application programs and peripheral devices such as hard disks, printers and video adapters. These instructions are stored in non-volatile memory as a permanent part of your computer. They are always available at specific addresses in memory, so all programs can access them to perform their basic input and output functions. 

4.3. Different BIOS Manufacturers 

IBM computers contain a copyrighted BIOS that only their computers can use; however, other companies such as Phoenix, Award, and American Megatrends have developed BIOS for other manufacturer's computers that emulate or mimic the IBM instructions without using the same code. If you use a non-IBM computer, the BIOS company's copyright message and BIOS version number are displayed every time you turn on your computer. 

4.4. BIOS Extensions 

BIOS extensions In the PC are extensions to the main BIOS that enable the computer to work with add-on devices such as hard disk controllers and EGA or VGA adapters. The ROM chips containing these extensions do not have to be located on the motherboard; they can also be on expansion boards plugged into the expansion bus. Any BIOS extensions needed to run these expansion boards are loaded automatically when you boot your computer.

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