Can't say anything about the HR processes of private companies, and they are kept a secret too, so nobody really knows.

I do however know a thing or two about public service, HR in public service holds quite a lot of money, because they are the ones that ensure that it is a fair and meritocratic process. The public service wants to avoid the fact that people can just get a job simply through connections with the hiring manager. What the HR does is to screen candidates that matches the requirements set by the hiring department, and this process is kept confidential from the hiring department. Once the candidates have been shortlisted, the HR will pass all the shortlisted candidates' credentials to the hiring department and the hiring department and HR will further refine it. Most of the time, this refining process don't do much, and the candidates are shortlisted for the interview. The HR will rank the candidates according to perceived fit from the resumes based on credentials, and in the Public Sector, the better candidates are interviewed first most of the time followed by the weaker ones. If all goes well, the hiring manager, with input from the HR, will then decide which ones to be shortlisted for the final round of interview, where they meet the directors. This is usually for formality because the hiring manager already knows who he/she wants. Once the final interview is done, the hiring manager will choose who he/she wants and the candidate gets an offer. If this candidate rejects the offer, the second choice candidate will be called up. HR will then negotiate salary and incentives, which in the public service, are independent of the hiring department and manager. So if you choose not to reveal your salary to your immediate superior, he or she wouldn't know. That is the beauty of HR in public service. Of course there are pros and cons to such a detached form of involvement by the hiring manager and department.