What is the difference between thread parallelism and asynchronous operations in programming?

Thread parallelism and asynchronous operations are different approaches to task execution, although they sometimes overlap.

• Thread parallelism means the simultaneous execution of multiple threads on different CPU cores. This allows multiple operations to be performed at the same time, improving performance in multitasking.

• Asynchronous operations are a way of organizing code where tasks are started and executed without blocking the main thread, and the result is processed later (for example, through callbacks, promises, or async/await). Asynchrony does not necessarily mean parallelism: operations can be executed sequentially but without blocking the UI.

Example:

• In iOS, an asynchronous call can use GCD (Grand Central Dispatch) to perform a task in the background thread without blocking the UI.
• Parallelism is achieved if multiple threads are actually working simultaneously on different cores.

Thus, asynchrony is about non-blocking execution, and parallelism is about simultaneous execution.