Can you explain what is meant by the term 'lock' in the context of multithreaded programming?

In multithreaded programming, the term "lock" refers to a synchronization mechanism that allows limiting simultaneous access of multiple threads to a shared resource or critical section of code. This prevents race conditions and ensures data correctness.

For example, in C#, the lock keyword is often used for locking:

private readonly object _locker = new object();

void UpdateData()
{
    lock(_locker)
    {
        // Code that should only be executed by one thread at a time
    }
}

Here, if one thread enters the lock block, other threads attempting to enter the same block with the same _locker object will wait until the first thread exits the block. This achieves sequential access to the resource.