Who is Mark Renton from the motion picture, Trainspotting?

Mark Renton is a smart young man with a major drug problem. Renton is addicted to heroin and totally immersed in Edinburgh, Scotland's, underground drug culture. Renton crashes in a small, untidy apartment with his friends, all of whom live in anticipation of their next hit. They go out at night to clubs, but for the most part, their everyday lives revolve around their drug use.