Thanks for ur suggestions,
http://vx.netlux.org/lib/?lang=EN helps lot to understand the basics.

In my four hrs study, If we want to working of basics of virus via program

we need to do is,
Study the exe* file format ( *any file format virus infects)
study asm it will help how commands executed low level. It will help us
How the virus code get into the other file without disturbing the functionality of the original file.
Most important OS internels help us how process executed and the memory protection techniques... etc.

-lok.