Building a Virtual Machine, JVM-inspired (Intro)

Have you ever wondered how the Java Virtual Machine (JVM) works under the hood? While the real JVM is an incredibly complex piece of software, we can learn a lot by building a simplified version ourselves.

In this series, we’ll create a tiny virtual machine that demonstrates core concepts like thread management, multithreading, memory models, mutex, compilation, byte-code execution, function call stacks, both local and global scopes (heap), and even garbage collection.

What we are going to build

We are going to build a simplified virtual machine called TinyVM. The name TinyVM simply reflects its minimalistic implementation and is not a reference to any existing projects.

We’ll implement it in several parts to focus on one concept at a time. We’ll use C language to mimic JVM functionality, with detailed explanations of the code.

Part 1 — Foundations

• Variable assignment and manipulation with integer values
• Basic arithmetic operations between variables
• Console output functionality (print function)
• Thread sleep operations

Part 2 — Multithreading

• Implementation of real threads for concurrent code execution

Part 3 — Heap

• Implementation of globally shared variables accessible across all threads

Part 4 — Synchronized

• Implementation of mutex (mutually exclusive locks) to prevent race conditions in concurrent threads

Part 5 — Refactoring

• Code organization into modules like core, instructions, memory, thread, etc.

Part 6 — Functions

• Support for both synchronous (sequential) and asynchronous (threaded) function execution

Part 7— Compilation

• Introduction of byte-code compilation support

Part 8 — Byte-code execution

• Implementation of byte-code loading and execution

Part 9 — Function call stack

• Implementation of function call stack for tracking execution order in chained functions

Part 10 — Garbage collector

• Implementation of a basic mark-and-sweep garbage collector to automatically manage memory and clean up unreferenced objects

What we won’t build

To maintain focus on thread management, the following features will not be implemented:

• Class loading and Java parsing/compilation to byte-code
• Complex data types (integers only)
• Exception handling
• Performance optimizations
• Advanced programming practices

The short sum-up to read

Before continuing with building our Virtual Machine, I recommend reading about JVM’s basic building blocks, memory organization, and thread operations in this article:

A Deep Dive into JVM Memory Architecture and Thread Interactions

Next steps

1. Part 1 — Foundations
2. Part 2 — Multithreading
3. Part 3 —Heap
4. Part 4 — Synchronized
5. Part 5 — Refactoring
6. Part 6 — Functions
7. Part 7 — Compilation
8. Part 8 — Byte-code execution
9. Part 9 — Function call stack (not started)
10. Part 10 — Garbage collector (not started)