Hi Hamid,
I'm not an expert but when I began "to play" with PICbasic I've found that Proton+ (former PICbasicPlus) was easiest for me.
You can find Proton+ under the name PICbasic Plus probably in this forum or with eMule. The last "free" version was 2.1.3 .
Also, you can find Proton+ under the name Proton+ DS (Developmente Suite) which Compiler version is 2.2.0.20 in this forum but I'm trying it and I've problems as, for instance, it does not support includes, that's not a big problem but...
Finally, the're another Proton+ DS with the compiler version 3.0 and you can find it in this forum but it has restriction.
So, if you're an "amateur", begin with the Proton+ 2.1.3 (remember it's called PICbasic Plus, too), if you're an "expert" try the Proton DS releases and tell me your experiences
.
Any way, browse this forum to know the restrictions of both Proton+ releases (one is from Rego and the otherone is from Posek Group).
Good luck!!
Breixo