The document discusses the Java Virtual Machine (JVM), highlighting its role as an engine for executing Java code and its ability to create system-independent programs. It outlines the fundamental components of the JVM, including bytecode compilation and conversion into machine code, and also addresses its drawbacks, such as additional memory consumption and lack of operating system optimization. Various implementations of the JVM, including Microsoft, Netscape, and Sun, are noted along with their support for Java core classes.

2. Topics
 Java Virtual Machine.
 Why JVM?
 Java Runtime Environment.
 How JVM work?
 JVM Fundamental Parts.
 Process of compilation.
 Process of converting byte code into machine code.
 Diagram of JVM.
 Current JVM.
 Drawbacks of JVM.
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3. Java Virtual Machine
 JVM is a part of java programming language.
 JVM is the engine that drives the java code.
 Mostly in other programming languages, complier produce code for a particular
system ut Java cier produce Bytecode for a java virtual machine.
 JVM is a software, staying on top of Operating System, such as UNIX, Windows
NT.
 It create the environment that java language lives.

4. Why JVM?
 An ordinary language can not create a system independent program.
 Java’s goal is “Write-Once-Run-Anywhere” .
 Java program are not computer, Operating system dependent.
 Need to create an”Abstract Computer” of its own and runs on it, a kind of virtual
machine which hiding the different OS implementation.

5. Java Runtime Environment
Java Runtime Environment(JRE)
Java API classes
Java Virtual Machine
Operating Systems(Windows, UNIX, etc)
Hardware (Intel, Alpha, Motorola, etc)

6. How Java Work?
 Java programs are compiled into bytecode.
 JVM interprets and converts java bytecode into machine code in order to execute on a
CPU.
 Most web browser has an integrated JVM to run applets.
Other JVM tasks include:
 Object creations of java programs.
 Garbage collection.
 Security responsibility.
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7. JVM Fundamental Parts
 A bytecode instruction set.
 A set of registers.
 A stack.
 A garbage-collected heap.
 An area for storing methods.
All five parts are necessary, may be implemented by a complier, an
interpreter or a hardware chip.

8. Process Of Compilation
Java
program
Java
complier
Virtual
Machine
Source code Byte code

9. Process Of Converting Bytecode Into Machine Code
Byte code
Java
Interpreter Machine code
Virtual machine Real Machine

10. Diagram Of JVM

11. Drawbacks Of JVM
 JVM is a layer on the top of your operating system that consumes additional
memory.
 JVM is additional layer between complier and machine.(Comparing java program
and fast C program!)
 Byte code is compied for system independence so it does not take advantage of any
particular operating system.

12. Current JVM
 Microsoft Java Virtual Machine.
 Netscape Java Virtual Machine.
 Sun Java Virtual Machine.
 All of these java virtual machines implement java core class packages and their own
specific class packages.

13. THANK YOU!