Most low-end robitics seems to involve kits that are fairly fixed-function.

A step above that you can find kits and assemble your own based on building blocks. These often use a microcontroller and you program them in fairly raw C or a "Tiny Basic" variety of control programming language. Doing much more than the fixed-function kits can be a lot of frustrating work. There is no OS and few OS-like functions in the available libraries, so you have to write quite a bit of fiddly low-level code.

Above that you can find a few, more expensive, setups based on a stripped Linux or WinCE. The WinCE packages often have the Compact Framework and have larger hardware requirements and cost than the Linux versions. I'm not sure what might be available anymore - they weren't too successful. The Linux setups typically rely on C or a scripting language, and in some cases a small JVM allowing a Java compiler to be used but providing a limited set of libraries.

From what I've read I'd guess that the actual automated probes which get sent into space are based on a real-time OS kernel and not Linux or WinCE. The actual programming probably consists of libraries written in C called by "programs" (really a list of functions called by the "executive" i.e. the kernel) that are either threaded code (a la Forth) or p-code (e.g. bytecode, IL, etc.). Both of those tend to be very compact compared to fully-compiled machine code.

Then above that you have people using full-blown OSs such as a complete Linux, BSD, or NT. These offer advantages in simplifying the programming, offering a vast array of libraries to do your heavy lifting as well as a wide choice of programming languages. They also support absurdly large RAM, CPUs, and mass storage. However nobody seriously does much robotics work this way, the stuff weighs too much (especially when you add in batteries), costs too much, tends to be fragile, and is more likely to fall over when you need it the most.


One way to get into it for cheap, assuming you already have a PC to do the coding and compiling on, was a device called the Spy Video Trakr. This was a "remote controlled car" sort of toy that could send video back to the controller. But there was also a sort of macro language to create simple programs ("missions") and an SDK to program it in more detailed fashion in C. It isn't on the market anymore, mainly because people lost interest when they found out how much work it was to really program the thing. You might pick up a unit for cheap on eBay or someplace though, I'm sure lots of them are being dumped by people who had no idea what they were buying. The SDK is still available for download:

http://www.spygear.net/help/apps.php

So your out of pocket cost ought to be well under $80 for the whole unit.

Anything more sophisticated is going to turn into a hobby for the "live in Mom's basement and she lets me use her credit card" set. Expect to invest well over $500 in hardware and tools just to get something basic going.