🧠 What is IPC?
IPC (Inter-Process Communication) is a set of mechanisms provided by the operating system that allows processes to communicate and coordinate with each other — either on the same machine or across a network.
Since each process has its own private memory space, they can’t directly access each other’s data — IPC provides the controlled pathways for that.
🔁 Why is IPC Needed?
| Reason | Explanation |
|---|---|
| 🔗 Data Sharing | Processes often need to exchange results or inputs |
| 🧠 Coordination | Synchronize actions (e.g., client-server model) |
| 🛑 Resource Sharing | Handle shared access to devices, files, etc. |
| 🚦 Synchronization | Ensure correct execution order (avoid race conditions) |
🧰 Types of IPC Mechanisms
1. 📨 Message Passing (No shared memory)
| Method | Description |
|---|---|
| 📮 Pipes | Unidirectional byte stream between related processes |
| 🔄 Named Pipes (FIFOs) | Bidirectional and can work between unrelated processes |
| ✉️ Message Queues | Kernel-managed message buffers |
| 🌐 Sockets | For network-based communication (e.g., client-server) |
2. 🧠 Shared Memory (with synchronization)
| Method | Description |
|---|---|
| 📦 Shared Memory Segment | Common memory region mapped into multiple processes |
| 🧵 Semaphores | Used to synchronize access to shared memory |
| ⛓️ Mutexes / Locks | Prevent concurrent writes/read-conflicts |
| 🪢 Memory-Mapped Files | Shared memory via mapped files (e.g., mmap()) |
🔍 Message Passing vs Shared Memory
| Feature | Message Passing | Shared Memory |
|---|---|---|
| 🔗 Speed | Slower (involves kernel) | Faster (direct memory access) |
| 🔐 Complexity | Easier (OS manages sync) | Needs manual synchronization |
| 📚 Use Case | Distributed systems | High-speed local communication |
🧪 Example (Linux)
// Example: Anonymous pipe (Parent-child)
int fd[2];
pipe(fd);
fork(); // Child process
// One writes to fd[1], the other reads from fd[0]
⚙️ Real-World Analogy
Think of processes like people in separate rooms.
IPC is the phone line, shared whiteboard, or message tube between them — they can’t see each other’s notes, but they can send messages or share a board.
🧠 Interview-Ready Definition
Inter-Process Communication (IPC) is a collection of mechanisms provided by the OS to allow processes to communicate, coordinate, and share data. It includes message-passing tools like pipes, sockets, and message queues, as well as shared memory with synchronization primitives like semaphores and mutexes.