Is Hindi our National Language?

I never knew that Hindi was not our national language till a few months ago.All my entire life till then what I thought was that Hindi was our national language.I remember very well learning that Hindi is our national language or Hindi hamari rahtra bhasha hai.Even now also I had an argument with one of my friends that's how I ended up in googling it and found out this fact.According to the constitution of India there is no national language but it says that the official language of the Union shall be Hindi in Devanagari script. So Hindi is our first official language and English is the second.Neither the constitution nor law specifies a national language.Hindi got its staus given the large number of people who speaks it and the usual politics involved making it as so.Though Dravidian languages have a history independent of Sanskrit, eighty percentage of Malayalam words are taken from Sanskrit.So next time if any one argues with you that make it clear to them that Hindi is not our national but an official language.