we need a Caesar cipher-decoder. with any step.

[JuliaRossa]

the program must have an interface , it must encrypt and decrypt. Help please.

 

[Skydiver]

We are not a code writing service. If you post your existing code and tell us what problem you are running into, we can help you work things out. We won't do your work for you, though.

 

[jmcilhinney]

This is clearly a homework question so you appear to be trying to get us to cheat for you. As suggested, we're more than happy to help you with actual issues you encounter when trying to do the work for yourself. If you just expect us to do the work though, then you'll be disappointed. We tend to help people mostly to help them learn to be better programmers but the best way to learn is to do. Trying and failing is a critical part of the learning process so if you're not prepared to try then there's not really anything for us to help with.