I'm reading a programming book and in it it is said, of a subset of engineers,
"Electrical engineers and systems designers who create computer motherboards and other hardware systems incorporating Intel processors need to know some of the rest, but they are a small and hardy crew, and they know who they are."
I unsuccessfully tried to find the meaning of that last bit on its own online. It seems to be an idiom. I would guess that it means that due to the small size of the group, the prominent people in it are known to one another and comprise a sort of community. Perhaps someone knows/has encountered the segment in question?
Best Answer
The phrase "they/you know who they/you are" is typically used to address members of a subset of your audience without specifying their names.
We often use this phrase in an acknowledgement, or dedication, like you might find at the beginning or end of a book. An example would be:
In other words, those people who supported me know that they are included in the group "all the people who supported me", so I'm not going to list each of their names.
Another common use - and one that perhaps makes more sense - is when you're admonishing a group of people in public, but want to spare them the embarrassment of being singled out. For example:
Similarly, you might use this phrase when giving a public address because you want the general audience not to worry that you might be talking about them:
In the quoted example, the author intends to say something like this:
The next section is not for everyone. It's only for people who need to know extra information about [whatever the next section is about]. The people who need to know this information are electrical engineers and systems designers who create computer motherboards and if you were a member of this group, you would know you were a member. So if you're not sure if this next section is for you, it's not.