i could not understand whether linux operating system is virus free or not?
if yes then please be descriptive?

Try a search of LQ on the subject. It's an often asked question

Linux is virus-free. I don't know how to get any more descriptive than that. There are "proof of concept" viruses, but none are effective unless you run as 'root' all the time and even then you usually have to manually invoke the virus to get things started. Personally I wouldn't even call that a virus - I think of a virus as being something like the flu - you don't have to do anything except get close to someone who's infected and you get the virus and there's nothing you can do about it.

Now rootkits - that's a different topic.

Exactly how much description of the viruses that it doesn't have do you want?

There are two additional observations that I have made in this regard:

1) Linux is "open source" (or similar) -- the thing is, it would be more difficult to hide a piece of malicious code in a program that anyone (including potential employers) could read.

2) Microsoft and Apple seem to depend very highly on scanning for viruses, but are slow to patch the vulnerability. There appears to be a greater emphasis on patching and prevention, than waiting until an attack occurs in Linux.

Millions of eyes on the code can make a big difference. Are there are any experts out there that would like to correct or comment on this?

The truth is that there usually aren't millions of eyes on the code; programmers are too busy to look at so much code so they only look at the tiny bit that they're interested in. I know almost 200 people who use Linux, and of that lot maybe as many as 5 ever bother to read any code. In the few projects I've sent patches in for, I haven't even bothered to look at the vast majority of the code - just the tiny bit which I wanted to fix. However, there usually is at least 1 other person who reviews the changes. The Linux kernel is one of the more unusual projects in the effort put in to review code and so on, so it would take some effort to get malicious code in there; however, not all projects run like that.