The terms refer to the language behavior in the multi-language environments, when the elements from two or more sources are used in the language communication. They are often used interchangeably, but, if used precisely, the code switching implies more the performance, while the code mixing - the (in)competence. One code is conscious or deliberate, the other one is not. For instance, the bilingual children go through the mixing at their early stages of development. For the code switching a perfect example is right in front of you ! Arabic is the largest case of diglosia in the world and in such an environment code switching is the normal language behavior. When you intentionally use fus7a while speaking amiya that is the code switching. Moroccans make the situation even more complex by adding the French elements.

Yes - one mixes, one switches. Switching suggests a deliberate action.

an error - I do not know how to remove this ...

@prof B: I hope that this is a joke!!! how can so who attended uni and claims to be an english teacher not explain the linguistic terms of code mixing and code switching?

I can mix and switch from English to Lithuanian within seconds.