JVM is software that is platform specific.
For example: Linux platform
You require a Linux based JVM, for windows platform you require a windows based JVM. Now in these days JVM is bundled with Internet explorer and With other types of browsers. JVM is a platform-independent execution environment that converts Java byte code into machine language and executes.

Figure: Java Program Execution Flow

A JVM performs the following tasks:

JDK(Java Development Kit)

JDK: JDK is a software package which is used to develop and deploy java applications.
JDK= javac compiler + .jar (libraries) + javadoc + jdb + JRE :

JDK consists:

Terms	Descriptions
javac compiler	It is use to convert .java file into .class file
JAR Files	A jar files are java API’s, which contains number of classes and interfaces. For Example to make a database connection with oracle we require ojdbc.jar.
Javadoc	through this utility we can make Java documentaion for any java program.
Jdb	jdb is a java debugger.
JRE	Java Runtime Environment

		//Step -1  Write Source Code
	class Demo
	{
		public static void main(String args[])
		{
		System.out.println ("Hello Java!");
		}
	}
	

//Step- 2 Save Code with class Name

Demo.java

//Step-3 Compile the code

javac Demo.java
(when you compile the code it will generate an intermediate code (Byte code) it is not a machine code.

//Step-4 run the Program

java Demo
(Run the program by starting the JVM with the Demo.class. The JVM translates the bytecode into something the underlying platform understands , and runs your program)



Procedure :

C:\Users\TechKnow>

C:\Users\TechKnow>H:

H:\>cd techKnow

H:\cd techKnow>javac demo.java

H:\cd techKnow>java demo

Output :

Hello Java!