What are the main components of JVM architecture?

JVM architecture breaks down into a small set of subsystems that work together to run a .class file: the Class Loader Subsystem, the Runtime Data Areas, and the Execution Engine, plus the native bridge that connects it to the platform.

1. Class Loader Subsystem - loads, links, and initializes classes.
2. Runtime Data Areas - memory regions such as the Method Area, Heap, JVM Stacks, PC Registers, and Native Method Stacks.
3. Execution Engine - runs bytecode using an Interpreter, JIT compilers, and the Garbage Collector.
4. Native Method Interface (JNI) - bridges calls to native libraries.
5. Native Method Libraries - platform-specific compiled code the JNI calls into.

flowchart LR
  A[.class files] --> B[Class Loader Subsystem]
  B --> C[Runtime Data Areas]
  C --> D[Execution Engine]
  D --> E[Native Method Interface]
  E --> F[Native Libraries / OS]

These pieces hand off work in sequence: loading feeds the memory areas, and the execution engine reads from those areas to actually run the program.