The information provided by Murthy in the very first post above is, I venture to say, misleading if not outright wrong. By most interpretations of immigration law, a person will not automatically drop out of non-immigrant status by virtue of filing I-140/I-485. Attorney Murthy uses the words 'converts to an adjustment applicant'. This is misleading, because an "adjustment applicant" is not a status like the F-1 is, so you can't really convert from one to the other. In reality, you become both an adjustment applicant with an underlying status of F-1. What is true is that one becomes ineligible to extend/renew/be admitted to the US under F-1 (non-immigrant) status.
The hooyou.com link provided above is much more accurate.
The hooyou.com link provided above is much more accurate.