Explain the main differences between synchronous and asynchronous process execution modes.

Synchronous execution mode means that a process or thread performs tasks sequentially, waiting for each operation to complete before moving to the next. In this mode, execution is blocked until the result is received.

Asynchronous mode allows launching operations without waiting for their completion and continuing with other tasks. The results of asynchronous operations are processed later, for example, through callbacks, promises, or async/await.

Main differences:

• Blocking: Synchronous code blocks the thread, asynchronous does not.
• Performance: Asynchronous mode is more efficient when working with input/output operations, allowing to avoid idle waiting.
• Complexity: Asynchronous code is more difficult to understand and debug.

Example in Swift:

// Synchronous call
func fetchData() -> Data {
    // blocks the thread until data is received
}

// Asynchronous call
func fetchDataAsync(completion: @escaping (Data) -> Void) {
    DispatchQueue.global().async {
        let data = ... // data retrieval
        DispatchQueue.main.async {
            completion(data)
        }
    }
}

In iOS, asynchronous operations are often used for network requests and UI work to avoid blocking the main thread.