Conditional variables will not be stored in memory?

when watching Modern operating system, there are the following:

conditional variables (unlike semaphores) will not exist in memory . If you send a semaphore to a semaphore that no thread is waiting for, the signal will be lost

I would like to ask you, does not exist in memory , can you explain this sentence in detail? thank you. Many of them have not been introduced in this respect

Operating-system multithreaded mutex

Jul.19,2021

you can refer to this article: https://www.cnblogs.com/catch.

to put it simply, when a wait is called, the signal called before it will not take effect on the wait call, because these condition variables will not be saved by the system.

that is, the condition variable specified when calling signal is discarded after the call, and the system will not save it.

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