How does a E-mail work ?

Just as a letter makes stops at different postal stations along the way to its final destination, e-mail passes from one computer, as a mail server. To another as it travels over the internet. Once it arrives at the destination mail server, it is stored in an electronic mailbox until the recipient retrieves it. This whole process can take seconds, allowing you to quickly communicate with people around the world at any time of the day and night 

Features of E-mail

•     .One-to-one or one-to-many communication
• ·       Instant communication
• ·        Physical presence of recipient is not required
• ·        Most inexpensive mail service, 24hr a day and seven days a week
• ·        Encourages informal communication

                                       At last created a logo for our blog 

Internet--------the history

In  1969, the U.S. Defence Department funded a project to devlop a network. Which can withstand the bombing. Basically the idea was to develop a very secured network which can work even after a nuclear attack. This project was known as ARPANET. The proposed network was not supposed to have a central control-which would be an obvious target. Ten years of research brought local area network LANs. 

E-commerce

Electronic commerce or e-commerce as it is popularly know refers to the paperless exchange of business information using electronic data interchange, electronic bulletin boards, data interchange, electronic funds transfer and data network based technologies. 

Just love designing characters

Ø  Topology

The geometric arrangements of a computer system. Common topologies include bus, star and ring.

Ø  Protocol

The protocol defines a common set of rules and signals that computers on the network use to communicate. One of the most popular protocol for LANs is called ethernet. Another popular LAN protocol for PCs is the IBM token ring network.

Ø  Architecture

Networks can be broadly classified as using either peer-to-peer or client/server architecture.

Computers on a network are sometimes called nodes. Computer and devices that allocate resources for a network are called servers.

computer network

Types of network

There are many different types of network. However from an end user point of view there are two basic types

Ø  Local –area network (LANs)

The computer are geographically close together (that is, in the same building)

Ø  Wide-area network (WANs)

The computers are further apart and are connected by telephones lines or radio waves.

In addition to these types, the following characters are also used to categorize different types of network.

Desktop

When you turn on your computer, the screen first displays basic input output information (BIOS) about your computer. Few seconds later window takes control and the windows logo flashes on your screen with the cloudy sky. You could see Microsoft windows98.” The first thing that always appear after loading is that you will be asked to type your password to entire windows. (it is the password you type the password first time when windows was launched

Operating system                                                         

An operating system is the most important system software and is must to operate a computer system. An operating system manages a computers resource very effectively, takes care of scheduling multiple jobs executions and manage the flow of data and instructions b/w the input and output

Language translator

A language translator is a system software which translates a computer programme written by a user into a machine understandable form.

The most elemental form of programming uses only the binary digits 0 and 1 which is directly understood by the electronic circuits.

Types of software

Computer software is normally classified into two broad categouries :-

(I)               System software

(II)              Application software

              System software

System software includes general programs written for a computer. It consists of pre written programs and documentation supplied by the manufacture along with the computer. These programs are held permanently in the machine. The primary objective of this software are to :

·        Enhance the efficiency of hardware utilised and

·        Make computer simple to use

What is software ?

As we know that computer is a machine which cannot do anything without instructions from the user. Din order to do any specific job you have to give a sequence of instruction to the computer. This set of instructions in a proper sequence of instructions is called a computer programme. Software refer to the set of programme that helps to run the hardware.  (computer system) to function in a desired manner. Hardware means physical components of the computer system.

Computer Language 

The language in which programs are written are called programming languages. These language can be classified into following categories.

• Machine language
• Assembly language
• High level language

Data processing system

The activity of data processing can be viewed as a system. According to james o’brien a system can be defined as a group of interrelated components that seeks the attainment of a common goal by accepting input and producing outputs in an organised process” for example a production system accept raw material  as input and produce finished goods as output.

                         INPUT ----------------------------PROCESSING--------------------------OUTPUT

There are many kinds of data processing system. a manual data processing system is one that utilizse tool like pen, and filing cabinets. a mechanical data processing system uses devices such as typewriter calculating machines and book keeping machines

The data processing cycle

The data processing activities are common to all data processing system from manual to electronic system. These activities can be grouped in four functional categories, viz., data input data processing data output and storage constituting what is known as a data processing cycle.

(i)                Input

The term input refers to the activities required to record data and to make it available for processing. The input can also include the steps necessary to check, verify, data contents.

(ii)              Processing

The term processing denotes the actual data manipulation techniques such as classifying, sorting, calculating, summarizing, comparing, etc. that converts data into information.

(iii)             Output

It is a communication function which transimts the information, generated after processing of the data, to persons who need the information. Sometimes output also include decoding activity which converts the electronically generated information into human-readable form.

(iv)             Storage

It involves the filling of data and information for future use:-

3d audio

3d audio is a technique for giving more depth to traditional stereo sound. Typically, 3d sound, or 3d audio is produced by placing a device in a room with stereo speakers. The device dynamically analyses the sound coming from the speaker so that it can readjust the sound to give the impression that the speaker are further apart.

3D audio devices are particularly popular for improving computer audio where the speaker tend to be small and close together. There are no of 3D audio devices that can attached to the computers sound card.

Plotter

Plotter is a device that draws pictures on paper based on commands from a computer. Plotter differ from printer in that they draw lines using a pen. As a result, they can produce continuous lines, whereas printers can only simulate lines by printing a closely spaced series of dots. Multicolour plotter use different coloured pen to draw different colour.

In, general, plotters are considerably more expensive than printer. They are used in engineering applications where precision is mandatory

Sound cards and speakers

An expansion board that enables a computer to manipulate and output sounds. Sound cards are necessary for nearly all CD-ROMs and have become commonplace on modern personal computers. Sound card enable the computer output. Sound through speakers connected to the board.     

Editing by our company asdevloper,com

Printer

Printer is a device that prints text or illustrations on paper and in many cases on transpransies and other media. 

Floppy Disk

It is similar to magnetic disk discussed above. it is 3.5 inch in diameter. the capacity of a 3.5 inch floppy is 1.44 mega bytes it is cheaper than any other storage device and is portable. the floppy is a low cost device particularly suitable for personoal computer system

Magnetic Disk

You might have seen the gramophone record, which is circular like a disk. and coated with megnetic material. megnetic disk used in computer are made on the same principle. It rotates with very high speed inside the computer drive . data stored on both the surface of the disk. Magnetic disks are most popular for direct access storage. 

Magnetic tape 

Magnetic tapes are used for large computers like mainframes computers. where large volume of data is stored for a longer time. In PCs also you can use tapes in the form of cassettes. the cost of storing data in the tapes is inexpensive. tapes consist of magnetic materials that store data permanently. It can be 12.5mm to 25mm wide plastic film-type and 500 meter to 1200 meter long.

Advantages of magnetic tapes 

1. Compact : A 10-inch diameter reel of tape is 2400 feet long and is able to hold 800, 1600 or 6250 characters in each inch of its length. the maximum capacity of such tape is 180 million characters. Thus data are stored much more compact on tape 

2. Economical : The cost of storing characters on tape is very less as compared to other storage devices.

3. Fast : Copying of data is easier and fast 

4. Long term storage : Magnetic tapes can be use for long term storage and a tape can be used repeadetily with out loss of data 

Practice questions ???????????

1. what are the four basic functions perfomed by the computer ?

2. what is scanner ?

3. choose the correct answer ?

(a) The task of performing arithmetic and logical operations is performed by -:

            (i) ALU       (ii) editor     (iii) storage      (iv) output

(b) The ALU and CU are jointly know as :

            (i) RAM   (ii)  ROM   (iii)  CPU   (iv) none of the above.

Mouse

Mouse is a device that control the moment of the cursor. Or pointer on a display screen it is a small object you can roll along a hard and flat surface. As you move the mouse the point on the display screen moves in the same direction. , mouse contain atleast 1 button and as more as 3

Light pen

Light pen is an input device that utilize a light sensitive detector to select object on display screen.

Speech input device

Speech or voice input devices convert a person s speech into digital form. These input devices, when combined with appropriate software, from voice recogination system. 

Digital tablet

This is an input device that enables you to enter drawings and sketches into the computer. A digitiging tablet consist of an electronic tablet and a cursor or pen a cursor (also called a puck) is a similar to a mouse, except that it has a window with cross hairs and pinpoint placements. And it can have as many as 16 buttons. A pen also called a (stylus) looks like a simple ball point pen.

Scanners

Scanner is a input device that can read text or illustration printed on paper and translate the information in to a form that the computer can use. A scanner works by digitizing an image – dividing it into a grid of boxes and representing each box with zero or one.

Magnetic ink character recognition (MICR)

An MICR identify character printed with a special ink that contain particles of magnetic material. This device particularly finds application in banking industry. Since the MICR system can recognise only certain character styles. The characters styles the characters have to be accurately formed.

Optical mark recognition (OMR)

Optical mark recognition, also called mark sense reader, is a technology where an OMR device senses the presense or tha absence of the mark, such as pencil mark. OMR is widely used in tests such as aptitude tests.

Bar code reader

These devices are gernealy available in super markets, bookshopes, etc. bar-code readers are photoelectric sacnners that read the bar codes of vertical zebra stripped marks, printed on a product containers. Supermarkets use a bar code system called the universal product code (UPC). The bar code identify the product tro the super market computer which has a discripation and the latest price.   

Input devices

An input device presents data to the processing unit In a machine readable form. Although the keyboard is a common input device for a small computer, a system may also support various other input devices such as optical character recogniation (OCR), magnetic link character recogniation (MICR), Mark sense reader, etc.

Keyboard

The keyboard is very much like a standard typewriter keyboard with a few additional keys. The basic qwerty layout of characters is maintained to make it easy for the trained typist to use the system. The additional keys are included to perform certain special functions such as loading a program, editing, a text etc. these are known as number keys that vary in number from system to system.

Optical character recognition

Often abbreviated as OCR, optical character recognition involve reading text from paper and translating the images into a form that the computer can manipulate. An OCR system enables you to take a or a magazine article and feed it directly into an electronic computer file.

How the CPU and Memory Work

The working of the CPU and memory is in various steps involved for multuplying two numbrs

1. the cantrol unit recognizes that the program has been loaded into the memory. it begins to execute the first step in the program.

2. The programe tells the user "enter 1st number"

3. The user type the number 100 on the keyboard . An electronic signal is sent to the CPU.  
            
4. The control unit recognizes this signal and routes the signal to an address in memory -- say address7

5. the user types the number 4 on the keyboard. an electronic signal is sent to the CPU

Arithmetic –logic unit (ALU)

Arithmetic Logic Unit, usually called the ALU, performs two types of operations- arithmetic and logical. Arithmetic and logical. Arithmetic operations are the fundamental mathematical operations consisting of addition subtraction, multiplication, division. Logical operations consist of comparisons. That is two pieces of data are compared to see whether one is equal to, less than, or greater than the other.

Memory

Memory- also known as the primary storage or main memory- is a part of the microcomputer that holds data to be processed, instructions for processing the data (the program) and the information (processed data).

                                       

Central Processing Unit (CPU)

The part of the computer that executes program instructions is known as, the processer or central processing unit (CPU). In a microcomputer, the CPU is based on a single electronic component. The microprocessor chip, within the system or system cabinet. The system unit also include circuit boards. Memory chips, ports, and other components.

The CPU has two parts---the control unit (CU) and the Arithmetic logical unit (ALU). In a microphone

Both are the microprocessor chip.

Cantrol Unit (CU)

The control unit tells the rest of the computer system how to carry out the programme instructions. It directs the movement of electronic signals b\w memory – which temporaily holds data, instructions and processed information – and the ALU. It also direct these cantrol signals b\w The CPU and input\output devices

  A computer does mainly the following four functions:

• Recive input -Accept data/information from outside through various input devices like the keyborad, mouse, sacnner, printer, etc
• Process information - Perform arthmetic and logical operations on data/information.
• Produce output -communicate information to the outside world through output devices like monitor, printer, etc
• Store information - Store the info in storage devices like hard disk, floppy disks, CD, etc

These are 4 basics functions responsible for everything that computer do. The hardware components of the computer specilaize in any one of these functions.

computer hardware fall's into two categerious: processing hardware, of consist of the central processing unit. and the phereprical devices.phereprical devices allow people to interact with the CPU.

Objective

1.1   objective

After going through this lesson, you will be in a position to:

·        Identify the basic components of a computer and there working

·        Explain the importance of various units of a computer

·        Learn how these units work together to accomplish a given job

1.2          Functions  and Components of a Computer

 To functions properly the computer needs both hardware and software

Hardware consist of the mechincal and the electronic device.  Which we

See and touch. The software consist of programme. The operating system

And the data that reside in the memory and the storage device.

About computer

(i)                Centeral processing unit (CPU): the brain of the computer. The component that

That actually executes instructions

(ii) Memory: it enables a computer to stroe. At least temporailly, data

     And programs

    (iii) Input devices: usually a keyboard or mouse is used to read data and

           Programs into the computer

(iv) Output device: a display screen, printer, etc. that lets you see what the computer has accomplished.

(v) Mass storage device:  it allows a computer to permanently store large amounts of data. Common mass storage devices include disk, drive, and tape drive

What is computer

                    Computer science

Anatomy of digital computer

1.1    Introduction

We should keep in mind that a computer is a programmable machine.

The two main characteristic of a computer are : (i) It respond to a specific set of instruction

In a well-defined manner. (ii) it can execute a per-recorded list of instruction (a program) . modern computer are electronics and digital. The actual machinery-wires transistors and circuits is called hardware. the instructions and data are called software. all gernal purpose computer require the following hardware components.