need a program to practice C++

Depends what you want to do for programming.

Personally, I prefer programming in vi which is a very basic but powerful editor (think notepad on steroids), but it has a learning curve of it's own.

You will need a compiler. Usying Synaptic (System -> Administration -> Synaptic), search for build-essential

Install that and all the dependencies needed by clicking "OK" then "Apply".

If you want an integrated development environment, kdevelop is good. Same process in synaptic (search for kdevelop , click ok, then apply).

As for code, you can either start from scratch, use a sample program (see below), or grab on to a currently running open source project which interests you.

GNU has an example program called hello, which teaches the basics of coding for things like multi language. More information is here:
http://directory.fsf.org/project/hello/

If you wish to join an existing project, you can install the -dev package. If you wanted to join a project, either download the .tar.gz from their home page (the most recent release version), follow their instructions for the SVN copy (this would be the most recent, and may not work and be very buggy)

-Allen

It depends on your knowldenge. There is not special program for practice in Ubuntu (well, I don't know any), but you can find many materials, tutorials, examples etc. on internet...

I don't program in C++, but I've been learning more Python by working through Project Euler (www.projecteuler.com). It is a site that has math problems that can only be solved by programming a solution. It is language agnostic, and there are many people on the site that use C++. I have learned a ton using the site. If you like math, I highly recommend checking out the site.