After crawling a site by Google crawler and analyzing their back links a site get ranking in Google. Google crawler a software which is run through Google algorithms which is not human editor. I want to know in Google a site get it ranking by manually also?
If I understand you correctly, you would like to know whether Google staff can manually rank a page or whether it's all automatic. In answer to that, I'm sure that it's possible, but with the number of sites on the internet worldwide, they're unlikely to manually change a site's ranking unless they have a seriously good reason to.
The boost is done automatically. Algorithms and all that, based on number of links, page rank, etc. If you experience a sudden PR drop, that usually means a manual penalty specially if you're doing paid links.
I think the boost is usually done automatically however, google has the power to manually change a site's rankings if that site is being penalized.
Manual penalties have become pretty common lately, so while google doesn't seem to boost rankings for quality sites manually, they penalize others...which pretty much leads to the same result.