how many hours a normal person can work on computer

Well it depends on the person but usually after couple hours you start to get back pains and a red eye. My suggestion is that every 30 minutes stand up and walk around and if possible look out the window into the daylight. This could really help you if you sit in front of the computer for your job.

Many years ago I worked on the PC non stop for three days and nights trying to create a Hotel Management program on FoxPro. I fell sick and had to admitted in hospital. I think anyone can work on PC nonstop for two nights and two days and not more than that. Much depends on one's stamina and perseverance too.

I think some eight hours is okay to sit in front of the computer and work on it, more will be a bit damaging to the eyes everyday, so maybe the eight hours is quite well enough.

I honestly have no idea. I suggest you rest every hour so that your eyes and body can relax.

11-12 hour i think. After that he or she is intend to face some problem like headache and other irritation problem in eyes.

I think I have heard that you should rest your eyes every now and then and also get up and have a walk every hour or two

when your in the front of computer you should 12 meters away from the monitor or more I think and also about 2-4 hours, you can search more info about it on internet.