1. Hardware Concepts

2. A computer performs basically five major functions irrespective of its size and make.
It accepts data or instructions by way of input
It stores data
It processes data as required by the user
It controls operations of a computer
It gives results in the form of output

6. Input Devices
These are used to enter data and instructions into the computer.

7. Keyboard
This is the most common input device which uses an arrangement of buttons or keys. In a keyboard each press of a key typically corresponds to a single written symbol. However some symbols require pressing and holding several keys simultaneously or in sequence.
Apart from alphabet keys (26 keys), there are several other keys for various purposes such as:
Number keys - The 10 number keys 0-9 are there on each keyboard.
Sometimes, there are two sets of these keys.
Direction keys - There are four direction keys : left, right, up and down which
allow the curser to move in these directions. Unlike alphabet and number
keys, these keys do not display any thing.
Function keys - There are generally 12 functions keys F1-F12. These keys have
special tasks and the tasks may change from program to program. Just like
direction keys, these too do not print anything.
Other keys - There are several other non-printable keys for various different
purposes. These include caps lock, tab, ctrl, pause, delete, backspace,
spacebar, shift, enter etc which are used for special purposes.

8. Working: Whenever a key is pressed, a specific signal is transmitted to the computer.
When a key is pressed, an electrical contact is formed. These electric signals are transmitted to a microcontroller in a coded form to the computer describing the character which corresponds to that key.
On the basis of KEYS-LAYOUT they are of two types
a) QWERTY Keyboard
b) Dvorak Keyboard

9. Mouse
It is one of the most popular pointing devices which are being used frequently to control cursor around the screen. It has two-to -three buttons that are used to select an object or opening a program. It is available in following types.
Wheel Mouse:
 It contains left, right buttons, and middle scrolling button as well that is used to page up/down means scrolling. The main thing is that it has a ball under it that rotates when a user has been dragging over there. In this way screen pointer is controlled.
Laser Mouse:
 It is very similar to the wheel mouse but the difference is that it emits a laser beam of light to get through mouse pad instead of rolling  ball, remaining other functions are same like wheel mouse.
Wireless Mouse:  
Such type of mouse does not require a cable to attach. It consists with internal battery like dry cell, so that it performs all other mouse functions using wireless technology.

10. Light Pen:
It is also a pointing device. We move it on the screen just like an ordinary pen but it works with electricity. It is used for drawing maps, pictures & also has no alphabetic keys. Simply it sends input to the computer when a user touches on the screen. That is why graphic designers & Engineers use it most of the time.
Joystick:
It is another computer input device having “Base” & “Stick” is known joystick. The stick is connected to the base, so the stick can move freely up to the 180 Degree that is used to move an object on the screen by moving it.
It provides beautiful functions & facilities to control video games around the screen. Therefore this one is very popular device among children.

11. Touch Screen: Scanner:
The touch screen is very reliable in these days; this input device is used in mobile phones and tablets. Now computer screens are also being changed by inserting touch system because it is very easy to use than key pressing.
Scanner:
It converts hard copy into soft copy. It scans any of written or image things and then converts into digital form.
Now a day latest scanners provide a facility of OCR stands for Optical Character Recognition. In fact, OCR is software that converts the document image into text format. So a user can edit it in Word Processor like MS Word.

12. Bar Code Reader
This device read the bar code as input data. It consists of a light source, a lens and a light sensor which translates optical impulses into electrical signals.
Also it contains decoder circuitry which analyzes the barcode's image data and sends the barcode's content
to the scanner's output port.
Biometric Sensors
It is used to recognize individuals based on physical or behavioral
traits. Biometric sensor is used to mark attendance of
employees/students in organizations/institutions. It is also
popular as a security device to provide restricted entry for secured
areas.

13. Microphone:
It is used to input audio data into the computer. They are mainly used for sound recording.
Webcams:
This captures video as data for computer with reasonably good
quality. It is commonly used for Web Chats.
In personal computers, a webcam is attached via USB but so many laptops & Mobiles have a built-in webcam.

14. Graphics Tablet
This device is used to enter data using a stylus. Most commonly it is used to enter digital signatures.
Smart card reader
It is used to access the microprocessor of a smart card.
Smart cards are used in
large companies and organizations for strong security authentication.

15. Output Devices
These are used to display results on video display or are used to print the result. These can also be used to store the result for further use.

16. Monitor or VDU
It is the most common output device. It looks like a TV.
Its display may be CRT, LCD, Plasma or touch
sensitive.
Speakers
These are used to listen to the audio output of computer.
Printers
Dot Matrix Printer : These are used to produce hard copy of output as text or graphics.This printer prints characters by striking an ink soaked ribbon against the paper.
These can be used to generate carbon copies also.

17. Inkjet/Deskjet/Bubblejet printers
These all are low cost printers which use a controlled stream of ink for printing.
Laser Printers
These printers use laser technology to produce printed documents. These are very fast printers and are used for high quality prints.
Plotters
These are used to print graphics. It is mainly used in computer aided
designing.

19. Communication Bus
. In computer architecture, a bus is a system that transfers data between computer components or between computers.
Address Bus
This is a system of bus, which is used to specify the address of a memory location. The width of a bus determines the number of memory locations that can be addressed.
For example a system with 64-bit address bus can address 2^64 memory locations.
Data Bus : This system of bus is a medium, which transfer the data from one place to another in a computer system.
Control Bus : This system of bus carries the signals that give the report about the status of a device. For ex one wire of bus indicates whether the CPU is currently reading or writing from the main memory.

21. A communication port is mounted in a slot on the computer for easy
plugging/unplugging of a peripheral device.
Serial Port
Through this port the information travels in and out one bit at a time. Serial ports come in
the form of 9-pin or 25-pin male connector. These ports are often known as
communication (COM) port.
Mouse, modem etc. are connected using serial port though now mostly they are been replaced by USB port.

23. Parallel Port:
Through this port the several data signals are sent simultaneously over several parallel channels.
Parallel ports come in the form of 25-pin female connector. These ports are used to connect printer, scanner etc.

25. RJ 45 Port: This port is used for Ethernet connections and can be used between computer and any networked device, such as a cable modem or a network hub. It is a 8 wire connector.
RJ 11 Port : This port is for connecting to a telephone line. It has six-wire conductors in it and is smaller than RJ45.
USB stands for Universal Serial Bus, used for short distance digital data
communications. This port allows data transfer between devices with little electric power.

26. Infrared Port
Bluetooth Port

29. Solid State Memories
The term ‘solid-state’ essentially means ‘no moving parts’. Hence Solid-state storage devices are based on electronic circuits with no moving parts (no reels of tape, no spinning discs, no laser beams, etc.) Solid-state storage devices store data using a special type of memory called flash memory. SSD, Solid-state drive (or flash memory) is used mainly in digital cameras, pen drives or USB flash drives.

30. Blue Ray Disk:
This is the latest optical storage media to store high definition audio
and video. It looks like a CD or DVD but can store up to 27 GB of data on a single layer disk and up to 54 GB of data on a dual layer disk. Where CDs or DVDs use red laser beam, the blue ray disk uses a blue laser to read/write data on a disk.

31. Types of computers : Analog, digital and hybrid
Digital computers based on size and performance are:

32. 1. Embedded Computers: These are computing devices which are inserted into circuitry of other electronics devices. e.g TV Remote control
2. Micro computers: They are the smallest digital computers that use a microprocessor as its CPU. These can be used as a stand alone machine and as a terminal in a multi-user environment. They are also known as Personal computers. Example – 1BM PC, APPLE Mac., etc
2. Mini computers: Mini Computers: These are better known as mid range servers as they can handle relatively small network of computers. Few hundred users can simultaneously login into these systems at a time. They had better processing and storage capacity than micro computers. Useful for small organizations. Example – VAX, DP-1, etc
4. Mainframe computers: They are general purpose computers capable of handling all types of scientific as well as business problems. Example – CDC-600, VAX 8842, etc
5. Super Computers: These are most powerful digital computers which support multiprocessing and parallel processing. These are extremely fast and accurate and are applied in complex computations like weather forecasting, space explorations etc. Its maximum speed is billions bytes per second. Example – CRAY3, PARAM 10000, etc.

33. Encoding is the process of converting data into a format required for a number of information processing needs, including:
Program compiling and execution
Data transmission, storage and compression/decompression
Application data processing, such as file conversion

34. 1. The American Standard Code for Information Interchange (ASCII)
A variety of encoding schemes are used to map the symbols of our spoken, mathematical, and graphical languages into numerical codes.
1. The American Standard Code for Information Interchange (ASCII)
The original ASCII character set included 128 "characters. The set included punctuation marks, upper and lowercase Latin alphabetic characters, the digits 0 through 9, and a set of control characters. The ASCII mapping of this character set to 7-bit numeric values was devised by the American National Standards Institute (ANSI) to simplify the task of connecting character-oriented peripherals (e.g., printers, teletype machines, monitors, etc) to computers built by different manufacturers.
In response to the growing need for representing new characters was the extension of the ASCII character set from 128 to 256 characters.

35. 2. Indian Script Code for Information Interchange (ISCII)
is a coding scheme for representing various writing systems of India. It encodes the main Indic scripts and a Roman transliteration. The supported scripts are: Assamese, Bengali (Bangla), Devanagari, Gujarati, Gurmukhi, Kannada, Malayalam, Oriya, Tamil, and Telugu.
In 1991, the Bureau of Indian Standards adopted the Indian Standard Code for Information Interchange (ISCII), the ISCII standard that was evolved by a standardization committee, of which C-DAC was a member, under Department of Electronics during

36. 3 Unicode Standard
The Unicode Consortium is a non-profit organization founded to develop, extend and promote use of the Unicode Standard, which specifies the representation of text in modern software products and standards.
Unicode enables a single software product or a single website to be targeted across multiple platforms, languages and countries without re-engineering. It allows data to be transported through many different systems without corruption.
Unicode is required by modern standards such as XML, Java, ECMAScript (JavaScript), LDAP, CORBA 3.0, WML, etc.
The Unicode Standard has incorporated Indian scripts under the group named Asian Scripts The Indian scripts included are Devnagari, Bengali, Gurumukhi, Gujarati, Oriya, Tamil, Telugu, Kannada and Malayalam. The Indian language block of Unicode Standard is based on ISCII-88.

37. E-waste The term "e-waste" is an abbreviation of "electronic waste".
"E-Waste is a term used to cover items of all types of electrical and electronic equipment (EEE) and its parts that have been discarded by the owner as waste without the intention of re-use."

38. E-Waste poses a threat to the environment, people and animals
E-Waste poses a threat to the environment, people and animals. Electronic products are jam-packed with heavy metals, semi-metals and various chemical compounds that can leak into soil and become hazardous. Things like lead, mercury, copper, barium, nickel and even arsenic are all present within a variety of electronic products.

39. E-waste disposal process
The e-waste recycling process is highly labor intensive and goes through several steps. Below is the step-by-step process of how e-waste is recycled,
Picking Shed
When the e-waste items arrive at the recycling plants, the first step involves sorting all the items manually. Batteries are removed for quality check.
Disassembly / Dismantling
After sorting by hand, the second step involves a serious labor intensive process of manual dismantling. The e-waste items are taken apart to retrieve all the parts and then categorized into core materials and components.
First size reduction process
Here, items that cannot be dismantled efficiently are shredded together with the other dismantled parts to pieces less than 2 inches in diameter.
Second size reduction process
The finer e-waste particles are then evenly spread out through an automated shaking process on a conveyor belt. At this stage, any dust is extracted and discarded in a way that does not degrade the environmentally.

40. 5. Over-band Magnet
At this step, over-band magnet is used to remove all the magnetic materials including steel and iron from the e-waste debris.
Non-metallic and metallic components separation.
The sixth step is the separation of metals and non-metallic components. Copper, aluminum, and brass are separated from the debris to only leave behind non-metallic materials. The metals are either sold as raw materials or re-used for fresh manufacture.
Water Separation.
As the last step, plastic content is separated from glass by use of water. One separated, all the materials retrieved can then be resold as raw materials for re-use. The products sold include plastic, glass, copper, iron, steel, shredded circuit boards, and valuable metal mix.

41.   Benefits of E-waste Recycling
Conserves natural resources: Recycling recovers valuable materials from old electronics that can be used to make new products. As a result, we save energy, reduce pollution, reduce greenhouse gas emissions and save natural resources by extracting fewer raw materials from the earth.
Protects Environment: E-waste recycling provides proper handling and management of toxic chemical substances like mercury, lead and cadmium contained in the e-waste stream.
Creates Jobs: E-waste recycling creates new jobs for professional recyclers and creates a second market for the recycled materials.  
Saves Landfills: E-waste recycling saves unnecessary dumps and landfills.