Computer Codes

1)   BCD (Binary Coded Decimal) Code:  This code is based on the idea of converting each digit of a decimal number into its binary equivalent in spite of converting the entire decimal value into a pure binary form. In this coding technique each decimal digit is independently converted to a  4 bit binary number which makes conversion process very easy.2⁴=16 configurations are possible but only first 10 are used to represent decimal digits from 0 to 9.

Character	BCD Code		Octal Equivalent
	Zone	Digit
A	11	0001	61
B	11	0010	62
C	11	0011	63
D	11	0100	64
E	11	0101	65
F	11	0110	66
G	11	0111	67
H	11	1000	70

Hard Disk Drive (HDD)

It is a data storage device and is made up of a thin circular discs, called "Platters", which are coated on both the sides by Magnetic Material. A Disk pack may consist of number of Platters and are mounted on a central shaft that rotates them in same direction with same speed.The Data is written or accessed in a random manner and individual blocks of data can be stored or retrieved in any order rather than just sequentially.It is connected to computer using different interfaces such as IDE, SATA or SCSI.

Information Storage: In HDD information is stored on all surfaces of platters except upper and lower surface of top and bottom platters respectively. thus,a  disk with 5 disk platters will have 8 recording surfaces. Each plotter is consist of no. of invisible concentric circles which are called tracks. A set of such corresponding tracks in all the surfaces is called cylinder. Tracks are further divided into sectors. * bit EBCDIC code is used for the information storage.The Information is stored in form of invisible magnetic spots. The Presence of magnetic spot represents binary 1 and absence represents binary 0.

OCR (Optical Character Reader)

This Device is used to detect alphabetic and numeric characters that are printed on the paper. These Characters can be handwritten or typed. These words must follow a standard size and no style should be used. If characters are typed than they must be typed using special OCR fonts. The standard OCR fonts are: OCR-A (American Standard) and OCR-B (European Standard).

Floppy Disk

It is a Magnetic type secondary storage media.It is Composed of a thin magnetic disk encapsulated in a rectangular plastic cover lined with fabric that is used to remove dust particles.They came in different sizes i.e. 8-Inch, 5.25-Inch and 3.5 Inch.The 8-Inch and 5.25-Inch floppy disks are obsolete now and only 3.5 Inch floppy is used rarely for the emergency start up of system or to update firmwares.Fig(1) given below shows a 3.5 Inch Floppy disk and various Parts of it.It mainly consist of Following Parts:

i)A hub that engages with drive motor
ii) A hole that identifies its capacity.
iii)A Shutter for protection,when removed from computer.
iv)A Plastic Housing
v)two polyester sheet to sandwich the magnetic disk in the middle to reduce friction.
vi)Magnetic coated plastic disk.
vii)A write Protection notch.

OMR (Optical Mark Reader)

It is a device that is used to read marked data from document forms such as tests or surveys.Some OMR devices uses dedicated scanner.It consist of a light source and light detector.When light falls on the paper it reflects it.Intensity of reflected light is more where paper is blank whereas darken areas of paper reflects less light.

In some OMR trans optic papers are used.when light is passed through paper,the intensity of light received at another end is low from darken areas and intensity is high from blank areas of paper.This combination of high low intensity is converted into binary values.OMR has the advantage that unlike OCR no complicated pattern recognition engine is required.Marks are constructed in such a way that their is no chance of error.

Computer Generations

First Generation(1942-1955)

This Generation is considered to be form 1942-1955. These Machines were designed with the help of vacuum tubes. The main features of this Generation Computer were:
1. Were designed with vacuum tube’s which was only electronic component available during those days.
2. These computers were fastest of their time and could perform calculations in milliseconds.
3. They were bulk in size due to the use of thousands of vacuum tubs.
4. These devices were non-potable and were more frequent to failure.

Characteristics of Computers

1) Speed: Computer is a very fast device it is capable of performing calculations in a few seconds that a human can do in entire month.

2) Accuracy: This is another Characteristic of computer that it performs all calculations with high accuracy. But this accuracy is dependent on its design and programming. If programming error occurs then result will also be affected by that.

3) No IQ: It is not a magical device and can perform only those tasks for which it is programmed or designed. But if it is designed with high class design then it can perform task with unthinkable speed and accuracy

How to Use Change Text Case in Office 2010 ?

1. Select the text for which you want to change the case.
   
   
   


2. Right Click on Selected text and select Font.

Identification of Computer Ports

Port Name	Used for Connecting	Looks Like
PS/2	Keyboard/Mouse
RS-232 or Communication Port or Serial Port	Used to Connect Serial Devices Such as Modem, Passbook Printer, KIOSK Machine, Ticket Machine etc.
LPT Port	Used to Connect Printer or Parallel Interface Devices.

Difference Between Volatile and Non-Volatile Memory

No.	Volatile Memory	Non-Volatile Memory
1	Volatile memory is computer memory that requires power to maintain the stored information.	Non-volatile storage is computer memory that can retain stored information even when not powered
2	Volatile memory retains the information as long as power supply is on, but when power supply is off or interrupted the stored memory is lost. Therefore it is used for temporary storage.	Non-volatile memory is typically used for the task of secondary storage, or long-term persistent storage.

Difference Between Hardware and Software

No.	Hardware	Software
1	All the Physical Units of Computer System to whom we can touch and feel are Hardware.	Software is a collection of  Programs and related data that provides the instructions for telling a computer what to do and how to do it.
2	Hardware is actual components that your computer is made of: RAM, ROM, Motherboard, modem, wireless chips etc.	Software is any Program that you can load onto computer.eg. Operating System (Windows, Linux) or games or any other applications.

Difference Between Computer and Calculator

Sr. No.	Computer	Calculator
1	A computer is an electronic device which can performs each and every task at a very high speed and high accuracy.	It is also an electronics device but it can do calculation work only.
2	A computer can work with numbers and words both.	A calculator can work only with numbers.
3	A computer can store large volume of data in its memory and reproduce any part of it, as and when needed	A calculator is not capable of storing data for long duration.