arduino library

I have been using Arduino for more than 4 years till now im using all free libraries available

How do i develop the library /CPP code for a particular sensor so that i can help others

Can anyone suggest some sources or specific example how to begin ?

that article could be a good start

I agree with J-M-L. That's a very nice tutorial.

The one thing to be aware of is that, although that tutorial is still very much valid, some additional features for Arduino libraries have been added since the time it was written, which might confuse you if you're using modern libraries as a reference. All that is documented in the Arduino Library Specification:

I don't necessarily recommend that you read the specification top to bottom, since it's likely that some of the information is of no use to you at this point. Just keep it in mind as a reference you can use to look up some specific bit of intormation you're interested in.