Differents versions of Asterisk

Hi all, i’m a french student and in order to make a rapport about Asterisk, i want to compare different versions of the software.

I would like to know what are the main differences between versions 1.2, 1.4 and if possible 1.6.

I hope somebody can help me because my search on Internet was successless.
Excuse me for my poor english

Adrien Bourroux

Go to asterisk.org and check the changelogs and upgrade files