I recently installed Ubuntu 12.04 LTS on my system dual boot with XP . My computer teacher at school used to tell that if a linux system is shutdown repeatedly it corrupts. I wanted to know that does same thing happen when it is done in ubuntu. Thank you.
Either your teacher was mis-informed, or the comment was used in a different context than you remember. In a controlled shutdown, the chances of any type of damage or corruption is extremely small. It is during forced, hard shutdowns that the chance of damage occurs - usually to open files and to the disk directory structure. This is applicable to any OS, not just Linux-based systems.
My kids shutdown Ubuntu by unplugging it about 50 time a day, and nothing happened so far. They also sometimes press the power button, to shut it down, and nothing so far.
No keep in mind that this be the case here, and doesn't mean that it safe all the time. From a professional point of view, eventually I will have to re-install, because the system is so corrupted, that's the only way to fix it.
As I'm typing this, one of them shutdown the laptop 5 times, by unplugging the cable, and Ubuntu just came back up, and she continued playing.