How can l use the one variable from one function in other functions?

Answer 1

If you just want to be able to use a variable everywhere, you can make it a global variable - declare it outside of any function.

(Normally we prefer not to do that.)

Answer 2

I'm not sure, if I fully understand your question, but...

You could work with pointers.

Maybe you want to elaborate?

Answer 3

Nothing new for me you are not amswered

Answer 4

Well, then, as Matthias said, ask your question in a less generic way so that we can understand what you actually need.