Basically, your question is "how are computer chips, instruction sets, operating systems, languages, libraries, and applications designed and implemented?"  That's a multi-billion dollar worldwide industry employing millions of people, many of whom are specialists. You might want to focus your question a bit more.

That said, I can take a crack at:

> I can't understand how people create programming languages and devise compilers for it.

It is surprising to me, but lots of people do look at programming languages as magical. When I meet people at parties or whatever, if they ask me what I do I tell them that I design programming languages and implement the compilers and tools, and it is surprising the number of times people -- professional programmers, mind you -- say "wow, I never thought about it, but yeah, someone has to design those things".  It's like they thought that languages just spring up wholly formed with tool infrastructures around them already.

They don't just appear. Languages are designed like any other product: by carefully making a series of tradeoffs amongst competing possibilities. The compilers and tools are built like any other professional software product: by breaking the problem down, writing one line of code at a time, and then testing the heck out of the resulting program.

Language design is a huge topic. If you're interested in designing a language, a good place to start is by thinking about what the deficiencies are in a language that you already know. Design decisions often arise from considering a design defect in another product.

Alternatively, consider a domain that you are interested in, and then design a domain-specific language (DSL) that specifies solutions to problems in that domain. You mentioned LOGO; that's a great example of a DSL for the "line drawing" domain. Regular expressions are a DSL for the "find a pattern in a string" domain. LINQ in C#/VB is a DSL for the "filter, join, sort and project data" domain. HTML is a DSL for the "describe the layout of text on a page" domain, and so on. There are lots of domains that are amenable to language-based solutions. One of my favourites is Inform7, which is a DSL for the "text-based adventure game" domain; it is probably the highest-level serious programming language I've ever seen. Pick a domain you know something about and think about how to use language to describe problems and solutions in that domain.

Once you have sketched out what you want your language to look like, try to write down *precisely* what the rules are for determining what is a legal and illegal program. Typically you'll want to do this at three levels: 

1. *lexical*: what are the rules for words in the language, what characters are legal, what do numbers look like, and so on.
2. *syntactic*: how do words of the language combine into larger units? In C# larger units are things like expressions, statements, methods, classes, and so on.
3. *semantic*: given a syntactically legal program, how do you figure out what the program *does*?

Write down these rules *as precisely as you possibly can*. If you do a good job of that then you can use that as the basis for writing a compiler or interpreter. Take a look at the C# specification or the ECMAScript specification to see what I mean; they are chock-full of very precise rules that describe what makes a legal program and how to figure out what one does.

One of the best ways to get started writing a compiler is by writing a **high-level-language-to-high-level-language** compiler. Write a compiler that takes in strings in your language and spits out strings in C# or JavaScript or whatever language you happen to know; let the compiler for that language then take care of the heavy lifting of turning it into runnable code. 

I write a blog about the design of C#, VB, VBScript, JavaScript and other languages and tools; if this subject interests you, check it out. http://blogs.msdn.com/ericlippert (historical) and http://ericlippert.com (current)

In particular you might find this post interesting; here I list most of the tasks that the C# compiler performs for you during its semantic analysis. As you can see, there are a lot of steps. We break the big analysis problem down into a series of problems that we can solve individually.

http://blogs.msdn.com/b/ericlippert/archive/2010/02/04/how-many-passes.aspx

Finally, if you're looking for a job doing this stuff when you're older then consider coming to Microsoft as a college intern and trying to get into the developer division. That's how I ended up with my job today!