Operating Systems Practice Test 1

An image-processing program splits its work between two workers. In version 1 each worker is a separate process created with fork(); in version 2 each worker is a thread created in the same process. In both versions, each worker writes its results into a global array results[].

In version 1 the parent never sees the workers' results in its copy of results[], but in version 2 it does. What explains the difference?