The Java Virtual Machine (JVM) is a software-based emulation of a computer that executes Java bytecode, which comprises opcodes and optional parameters. It facilitates the portability and security of Java applications and supports compilers for other programming languages, emphasizing a 'compile once, run anywhere' philosophy. The JVM handles class loading, memory management, and provides a comprehensive instruction set for various operations like arithmetic, object manipulation, and concurrency.

1. JAVA VIRTUAL MACHINE
Dhanith Krishna

2. Virtual Machines
A virtual machine (VM) is a software-based emulation of a
computer.
JVM executes Java byte code
Byte code is one byte op-codes followed by optional parameters
JVM platform is used by Python, Ruby etc
code execution component of the Java platform

3. JVM Architecture
•Better Security
•Portability
•Compile Once Run Anywhere
NEED FOR JVM

4. IS JVM for JAVA alone ?
• Compilers for other languages based on JVM exists
• Assemblers on JVM
•Erjang
•Rhino
•Free Pascal
•Quercus
•Jython
•NetRexx
•Jruby
•Jacl

5. • Loads class to memory
• Verification
• Allocation of static fields
• Linking
• Invocation of initialization codes
• Starting Main as a single thread
• Additional Threads are created using
Thread class
How class file works in JVM ?

6. JVM Architecture

7. Storage Management

8. Storage Management
Global Data – Global constant pool
Contains program constants and symbol table information
Per Thread Data – registers + stack + native stack
Heap – Dynamically allocated memory

9. Class File Format

10. JVM Instruction Set
•Load and store
•Arithmetic
•Type conversion
•Object creation and
manipulation
•Operand stack management
(push / pop)
•Control transfer (branching)
•Method invocation and
return
•Throwing exceptions
•Monitor-based concurrency