4.Introduction to Java Programming Language

Short History about Java :
Java is the Object Oriented Programming Language which initiated by James Gosling and Patrick Naughton in 1991.Initially its called OAK from oak tree that stood outside Gosling's Office then it was named as GREEN.Later given by the JAVA from Java Coffee.

Sun Microsystems released JAVA 1.0 in 1995.Oracle acquired Sun Microsystems in 27 January 2010 for $7.4 billion.Now we are having latest version as JAVA 7 which was released in the year 2011.

Features of Java:

Simple:

Unlike other programming language that provide dozens of complicated ways to perform simple tasks.Java provides  small number of clear ways to achieve a given task.

Secure:
Java has safety and security.Using java compatible browser , anyone can safely download Java applets(we will discuss it later.Applet is just an application like thing.no need to worry) without any fear of viral infection and no security will be breached.

Robust:
Robust means Strong.Most programs today fails for one or two reasons.

*Memory Management
*Exception Conditions

Java rectifies the problem of memory management by managing memory allocation and automatic memory deallocation by providing Garbage Collection for Unused Objects.

Java also handles exceptional conditions by providing object oriented exception handling.

Multi threaded:
Java supports multi threaded programming, which allows user to write programs that performs many functions simultaneously.

Architecture-Neutral:
"Write Once, Run anywhere, anytime, forever."(Platform Independent).

Interpreted:
By compiling code into an intermediate representation called Java Bytecode. This code can be interpreted(translate bytecode into machine code) on any system that has JVM.Performance by means of Just In Time(JIT) Compiler.

                                             

3.JAVA VIRTUAL MACHINE

Before we understand Java Virtual Machine, We will see Compiling and Linking process in C.

Here in the above figure, you can easily understand how compiling and linking process works in C language.I hope diagram itself is self explanatory..

Okay now where this a.exe gonna store....Obviously its gonna store in RAM as shown in below.

  It will store in RAM and starts execution.

Okay now coming to our part JAVA...There is no linking done in JAVA....See the image below..

Note: Class file which contains bytecode(intermediate code that is before machine code).

JVM (JAVA VIRTUAL MACHINE) Architecture :

 

JVM resides inside our RAM. There are three components inside our JVM.

1.CLASS LOADER

2.BYTE CODE VERIFIER

3.EXECUTION ENGINE

Class Loader Component loads class into the RAM. Byte Code Verifier for Security Purpose like checks whether there is stack underflow or overflow errors.And finally Execution Engine which contains Just In Time (JIT) Code Generator which is used to convert BYTECODE into native Machine Code and Starts its Execution. 

Difference Between JDK, JRE and JVM :

Many of the intermediate java programmers doesn't  know what exactly the difference between jdk,jre and jvm...Its very simple.

JDK is the acronym for Java Development kit.Inside JDK we are having JRE(Java Runtime Environment) and some Development tools.

JRE which contains some specific set of libraries and files.

JVM which we have already discussed which resides in JRE.

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How to Make Windows 7 Bootable Disc

I hope you might be having Windows 7 Image file...If you don't have, no need to worry...Click here to directly download Windows 7 ultimate 32 bit  and Click here to directly download Windows 7 64 bit...This is not a full version of Windows but we can make it as Full version....Contact me here  i will help you to make your windows as full version...

Okay now you have image file in your system...Now you want to make your DVD bootable...For this you need some application....Click to download Windows 7 DVD Tool...Download and  Install it in your system...After Installing, open the application..your application UI will looks like below...

Click Browse and select your image file and Click Next as shown in below....

then it will ask for media type, You dont worry about this...Just Click on DVD as below...

That's it...Wait for sometime to let it complete processing...then you will get your bootable DVD...if you have any queries,feel free to contact me...

USSD Balance Check for all Networks

For Vodafone :

To Know Account Balance and Validity : *141#

To know the Offers  : *121#(you may get discounts too)

To Know your plan details : *111#

To Know Data Balance : *111*6*2#

For Airtel :

To know the Account Balance and Validity : *123#

For  Airtel Money Recharge or pay bills : *400#

Offers in Airtel Money mobile recharge by *400# :

For 100, 110 Talktime.

For 500, 550 Talktime.

For 1000, 1100 Talktime.

For Bsnl :

To Know Account Balance and Validity : *123#

To 3G Data Balance : Message "USG to 53733" or "data 3g to 53733"

For Aircel :

To know Account Balance and Validity : *111#

To Know 3G data balance : *122*011#

Offers in Aircel--->Unlimited 3G data for 90 days only for 447 bucks...Only for Dongle Users...

2 GB/month for 3 months and post 2 GB speed will be reduced to 128 kbps...Browsing will be Good...

2.Assembly Language Overview

If we want to add two numbers in Assembly Language...

*Store 1 in Location A.

*Store 2 in Location B.

*Add Location A,Location B.

*Store Results.

you guys knows computer will understands in the form of binary representation...then how it can understands Assembly language?
So we need to convert Assembly Language into Machine Understandable Form(Machine Code)...okay you just look at the above figure...here you are passing some assembly language into assembler...Assembler's job is to covert/interpret into machine understandable form and giving machine code to respective processor...then you will get an result/output...

In the Above figure we are having another language named  "C"...C language uses the compiler to convert it (printf(a+b);) into assembly language...No need to worry about compiler now..I will definitely discuss about it later...

We may have different processors like Intel, AMD, Power PC etc...

to add two numbers the statement changes according to processors,

For Intel---->Add Location A, Location B
For AMD-->ADDITION Location A, Location B
For PowerPC--->Math.ADD Location A, Location B

For each processor we need different compilers in C...You may face problems with compatibility issues...So we use platform independent language named "JAVA".

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1.Some Basics Before Starting Java

Before we go forward to learn Java,we must know about Computers and how it understands user Input...

lets see....

What is Computer?

thinking........
"The Computer is an Electronic Device capable of  performing Computations."

We Human having Heart to live in this World...In the same way Computer must have some heart to live in this world...How it is possible?Even computer having Heart?you may ask me,hey santhosh are you gone mad,how could it be possible?

Yeah its Possible by using Processor...without Processor our system wont work... 

Okay santhosh,but you have written computer is an Electronic device then how  it can understand TEXT,IMAGES,AUDIOS and VIDEOS?
Great Question...I am having answer for this too...

Just look at this above diagram, Computer can understands only Electric signals...In our diagram we are passing 5 volt current, its simply binary 1...Similarly we are passing 0 volt current, its simply binary 0...Our Computer is continuously bombarded with these electronic signal/process...

*8 bits of such signals are grouped together..

*Symbol  "#" is represented by 10101010(8 bits)..

I hope you guys got it upto we discussed...Next we will see some overview of Assembly language...

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