F1 to adjustment to immigrant visa, possible?

[mariefa]

My friend said that his son entered the US 1991 on tourist visa then changed the status to F1 student visa (also 1991) with affidavit of support from his US citizen uncle.

Then after more than continuous 6 years of stay in the US (year 1997) his son applied for an adjustment of status to that of a lawful permanent resident because of continuous residency???

Is what my friend saying possible during those years??? Is it also possible today? What do you call this type of visa? Can his son really be adjusted to a green card even without US citizen petition.

Thank you very much!