Which programming language is the best to start learning/teaching about programming

From the shortlist I vote Python. Interesting alternatives (that I have at least some familiarity with) include Object Pascal, Modula 2, Ada, C#, Scheme, Objective CAML, F# and Haskell. I disagree with duros - I use C++ every day and I used C for years, but I don't see C-family languages as a good first choice. That includes Java, C# and Python - when you learn about pointers, it helps to make the pointer operations as explicit as possible - not hidden in the form of Java-like implicit references. For pointer stuff, I suggest a Pascal-family language first. Verbosity will be at least on a level with Java, though, and the lack of garbage collection is significant (not necessarily a disadvantage, but significant either way). C and C++ I'd reject on weak typing issues - implicit casts, which aren't always a good thing for learning in particular. Also, there's oddities like int *x, y; (y is an int, not a pointer-to-int) which can confuse. The comma operator probably catches everyone when they write their first switch statement, not to mention forgetting break. And C++ is just a huge language, with nice features true, but also with some real nasties. The one thing that might make me rethink that - Visual C++ Express Edition is free (in the beer sense) and very good. So good that you might want to consider it for running-in-the-debugger-as-a-teaching-tool reasons. The same applies to Visual C# Express Edition, of course. Most alternatives have issues in terms of convenient libraries. Python, Perl, Java and .NET languages (C# and F#) are hard to beat for that. Ruby probably belongs in that list, but I'm not very familiar with it. You may be able to work around some library issues for other languages by providing a "distro" of ready-built libraries with some automatic configuration, but this may involve quite a bit of work. For example there are libraries for just about anything for C++, but it takes a bit of research to select libraries, make builds of them that can link together compatibly, tell your tools where to find each library and so on. You can solve that to some degree with a "use Linux" policy, but the range of languages that get serious library support in Linux repositories is limited. Haskell in particular requires a very different skillset to more conventional languages, so should probably be disqualified unless you're are looking to teach that particular skillset. Other functional languages I've mentioned may also be rejected for similar reasons, though Objective CAML and F# are very plausible exceptions, capable of doing everything that conventional imperative languages can do with not-that-different syntax, but adding a range of tricks from the functional toolkit. F# also has the benefit of access to the .NET libraries. Perl, I'd reject simply because I don't like the language - not entirely for subjective reasons, but I still wouldn't want to have to defend that position. So - Python probably still gets my vote, but a Pascal-family language is probably better for learning pointers (Free Pascal or GCC Ada) and Objective CAML is a very interesting alternative (as is the closely related F#).

When teaching well educated adults programming as a cross-curricular thing, ie. science majors, maths majors, I find that it sinks in best if you approach it from a position they are comfortable with. Introducing programming via a language orientated to the sort of tasks they face like Mathematica, R, etc, with real world problems that they are aware of the methods to solve the issue and are aware of the need for a computerised solution. That way they tend to see the point of it, the transition is not overly confusing and they start to learn basic programming concepts via a form of osmosis. If they need to do something more complicated, then they can step up to something more traditionally broad in scope a lot easier than if they started there. Failing that, pick an easy to read, forgiving language with good feedback when you have made errors and easy debugging. Students get put off by a long road to results, instant/quick gratification is key to retaining enthusiasm.

How is a vector-based language a bad thing?! Especially if you're teaching beginners, you should focus on getting things done rather than worry about loop indices. Plus, R already has math and statistics routines built-in, which is exactly what you want in a "Scientific Computing" course. If you have your heart set on Python, at least use the http://www.scipy.org/ libraries. These will give you math routines as well as present a vector programming interface.

You're talking about a pretty specific environment, i.e. solving complex scientific or mathematical equations. I don't see where teaching the class using a general computing language (java, C#, etc) would be that beneficial, as they're not going to have the required syntax or library functions you're going to need. I don't see where teaching a particular language (or environment, like MathLab) is going to be a problem. Don't most IDEs or environments offer student pricing? Sorry, the question led me in the direction of that specific environment, if you're talking about a general computing environment, I'd go with teaching what is currently dominating the market to give them a feel for what is out there. I think thats currently either Java or .Net

As someone coding in Matlab on a daily basis as a researcher in biology, I do have to ask: What makes Matlab "not a real language" in your opinion? Its history of being good for numerical analysis? Because Matlab does fit all the requirements on your list, and the disadvantage #1 can be taken care of with a good set-up of the license server (I don't need VPN in order to use a license at home). Anyway, I guess that, in the end, the choice of programming language should really depend on the goals of the class. If what you want is give the students an idea of what they can do with programming, Matlab is great, because it's easy to write code, easy to debug, and the documentation is excellent. Python (with SciPy/NumPy/matplotlib) could be an alternative, but is a bit harder to get into than Matlab. If this is an introductory course for "general programming", after which they go on and learn a lot more programming, Matlab is not such a great choice, because students will not have learned to do declarations, they'll know nothing about pointers, and because they'll still start counting at 1.

I vote for Ruby for five reasons: It's designed for programmer happiness. It has the rails framework for those that like web and ui stuff. It has good testing frameworks. It encourages more 'human' readable code than java/C. [covers head] It's a good implementation of MVC. Excert: [from Wikipedia - http://en.wikipedia.org/wiki/Ruby_(programming_language)] Ruby is a dynamic, reflective, general-purpose object-oriented programming language that combines syntax inspired by Perl with Smalltalk-like features. It was also influenced by Eiffel and Lisp... supports multiple programming paradigms, including functional, object oriented, imperative and reflective. It also has a dynamic type system and automatic memory management...