Why the name “monitor”?

Question

I'm referring to monitors as described here:

http://en.wikipedia.org/wiki/Monitor_(synchronization)

None of the definitions here seem apropos:

http://www.thefreedictionary.com/monitor

So why are they called that?

== Update ==

Thank you for the answers, everyone!

I guess I was confused because I don't think of monitors usually as acting on themselves, which is what seems to be happening here. For example, you use a baby monitor to monitor a baby. I just don't think it would make much sense for a baby to monitor itself, but I could be wrong.

Answer 1

According to P. Brinch Hansen in Monitors and Concurrent Pascal: A personal history, the name originated from the original term for an operating system in the 60's and early 70's:

In the 1960s the resident part of an operating system was often known as a monitor. The kernel of the RC 4000 multiprogramming system was called the monitor and was defined as a program that "can execute a sequence of instructions as an indivisible entity" (Brinch Hansen 1969).

Answer 2

Take producer consumer problem for example. Without using a monitor, you'd have to constantly check whether the queue is 1) full or not and 2) empty or not by writing busy loop. In effect, the monitor monitors the state for you by transferring the control atomically.

Answer 3

I think that definition 3a (from the dictionary) comes close

3a. A usually electronic device used to record, regulate, or control a process or system

Answer 4

I think a monitor monitors (and controls) access to a resource.

Of the definitions at The Free Dictionary for Monitor:

Definitions 3A and 4 for noun apply, more or less (a monitor is not a program but a program component).

Definitions 1, 2, 5 from the 'verb, transitive' section could also be said to apply.