Concurrency and Synchronization

First let's understand some of the most confusing terms.

1. Multitasking

✅ Definition:

The ability of an operating system to run multiple programs (processes) at the same time by rapidly switching between them.

💡 Example:

• You are writing a Word document while listening to music and downloading a file — all at once.
• The OS switches between these apps so quickly it feels like they are running simultaneously.

🔧 Types:

• Preemptive Multitasking: The OS forcibly switches between tasks (used in modern OS).
• Cooperative Multitasking: Each task voluntarily gives up control (older systems).

2. Multithreading

✅ Definition:

The ability of a single process to be split into multiple threads that can run concurrently.

💡 Example:

• A browser (process) has:
  • one thread rendering the page,
  • another downloading data,
  • and another handling user input — all at once.

🔍 Threads share:

• Code, data, heap (same memory)
• But each thread has its own stack and registers.

3. Concurrency

✅ Definition:

The ability to handle multiple tasks by interleaving their execution — switching between them efficiently, possibly on a single core.

💡 Example:

• A single-core CPU running multiple tasks by pausing one and starting another rapidly — it looks like they’re happening at the same time, but they aren’t.

🔧 Tools:

• async/await, coroutines, cooperative multitasking, event loops.

4. Parallelism

✅ Definition:

The ability to execute multiple tasks at the exact same time using multiple CPU cores or processors.

💡 Example:

• On a quad-core CPU, 4 threads can literally run in parallel, each on its own core.