What happens inside a suspend function in Kotlin at the implementation level and how does it manage pausing the coroutine execution?

In Kotlin, a suspend function is a function that can be paused and resumed later without blocking the thread.

At the implementation level, a suspend function is compiled into a function with an additional parameter — a Continuation object, which contains the state of the coroutine and information about where to continue execution after suspension.

When a suspend function calls another suspend function or a suspension operator, the current coroutine saves its state (local variables, execution position) in the Continuation and returns control to the calling code. Later, when the result is ready, the coroutine resumes from where it was suspended.

Thus, control over suspension and resumption is managed through the Continuation, allowing asynchronous code to be written in a sequential manner without blocking threads.