Do drugs like provigil and modfanil make you smarter? Or are they like coffee? Do they improve working memory? Is there a potential for a pill like NZT from the movie Limitless?
Your question is very vague, and on a subject where a lot more research needs to be done, so forgive me but my answer is also going to probably be more vague and less definitive than you were hoping for.
Provigil, as far as I can tell is just another brand name of Modafinil, which has some very clear advantages when it comes to increasing your concentration and stamina. Military experiments show increases to precision and alertness in pilots after being awake for extended periods while on the drug compared to the control. Its actual capacity to increase your intelligence is harder to determine however. Some studies have shown it is effective, but in a meta analysis the benefits appeared to be mostly limited to those who did not have a high IQ to start with.
From what I have seen so far, Modafinil is more reliable as a stimulant. It can increase working memory and performance at a selection of tasks in some people, but is not a magic bullet for becoming a genius temporarily. In addition, it is not particularly safe for long term use. Other drugs with less severe side effects, and measurable long term side effects exist, but they are not nearly as dramatic. Piracetam and Choline are probably the best known and most widely studied combination for this.
As for NZT, there is unfortunately nothing at all like that yet and my speculation on the matter would be meaningless.