What every digit means in software version (1.7.1.0, for example)?

Question

What could every digit mean in software version? (for example, 1.7.1.0) How do you numerate your versions?

Thank you.

Answer 1

Every projects chooses its own convention. As others have pointed out, one common convention is "Major.Minor.Revision.Build"

A couple of my favorites are:

Ubuntu versions are "Year.Month". For example, 10.04 was released in April 2010.

TeX versions are theoretically only bux-fixes forevermore, so their versions are asymptotically approaching pi (e.g. 3.1415926)