Processes and Threads in Operating Systems
Welcome back to our Operating System series! In our last post, we explored different types of operating systems. Now, let’s dive into the core units of execution that an OS manages: Processes and Threads.
What Is a Process?
A process is simply a program in execution. Whenever you open a browser, play a game, or run a code editor — each action creates a process.
🧾 Key Difference: A program is a passive file (code), but a process is an active entity (running code in memory).
Key Characteristics of a Process:
- Has its own memory space
- Contains code, data, stack, and heap
- Managed independently by the OS
- Assigned a unique process ID (PID)
Example:
When you open Chrome and VS Code at the same time:
- Chrome = Process 1
- VS Code = Process 2
Both run independently, with separate memory and states.
What Is a Thread?
A thread is the smallest unit of execution within a process.
You can think of a thread as a lightweight process that shares the same memory of its parent process but executes independently.
Key Characteristics of a Thread:
- Shares memory and resources with its parent process
- Has its own registers, stack, and program counter
- Faster to create and manage than processes
Process vs Thread Comparison
| Feature | Process | Thread |
|---|---|---|
| Memory | Has its own memory | Shares memory with parent process |
| Overhead | More (heavyweight) | Less (lightweight) |
| Communication | Slower (needs IPC) | Faster (shared memory) |
| Dependency | Independent | Dependent on parent process |
Real-Life Analogy
Process = A company
Thread = Employees inside the company
- Each company works separately (process)
- Inside each company, multiple employees (threads) work on different tasks simultaneously
Life Cycle of a Process
A process goes through the following states:
- New → Created but not yet running
- Ready → Waiting to be assigned to CPU
- Running → Currently being executed
- Waiting → Waiting for I/O (like file or input)
- Terminated → Finished execution
Multithreading in OS
Modern OS allows multithreading, where a single process can have multiple threads running in parallel.
💡 Examples:
- A browser:
- One thread loads images
- Another handles user input
- Another loads the webpage script
Summary
| Term | Description |
|---|---|
| Process | Program in execution with its own memory |
| Thread | Smallest unit of execution inside a process |
| OS Role | Manages, schedules, and terminates processes/threads |
Final Thoughts
Processes and threads form the core of multitasking in operating systems.
Understanding how they work helps you debug faster, write better code, and build scalable systems.