Question about pointer in PCB structure and meaning of job queue
PCB structure exists inside kernel area. And in ready queue, which is Linked List, each Node of the queue is PCB.

This is correct, however in most operating systems, ready tasks are sorted by priority to ensure that the most important task will run next. So the design of the ready queue may be more sophisticated than this in practice.

Does PCB structure has pointer field that has address of next PCB structure??

This is the way that it's usually done. Of course, if it is implemented as a doubly-linked list, it will have a &quot;previous&quot; pointer too.

According to Wikipedia, Job Queue [...]

I can see why this may be confusing. The Wikipedia page that you're talking about is about batch processing systems. This is a related idea, and there are batch processing systems without user interaction, but it's not relevant to what you're trying to understand.