Question

As the title suggests, what is the default value of the maxConcurrentOperationCount for NSOperationQueue?

Is it set to a value of 1?

Answer 1

From the documentation,

The maximum number of concurrent operations set explicitly on the
receiver using the setMaxConcurrentOperationCount: method. If no value
has been explicitly set, this method returns
NSOperationQueueDefaultMaxConcurrentOperationCount by default.

So it is NSOperationQueueDefaultMaxConcurrentOperationCount. If this is set, it will choose an appropriate value based on the number of available processors and other relevant factors.

This is how it is defined:

enum {
  NSOperationQueueDefaultMaxConcurrentOperationCount = -1
};

NSOperationQueueDefaultMaxConcurrentOperationCount: The
default maximum number of operations is determined dynamically by the
NSOperationQueue object based on current system conditions.