by peterb
I hear this question a lot, typically from kids who have just discovered that there's more to a computer than a web browser, and who are curious about where to go for here. The people who ask this question typically don't have any specific project in mind; if they did, it would be a lot easier to answer them. Instead, they're really saying "I don't know much about programming, but I think it might be kind of fun. Where's the best place to start?"
An experienced programmer on a dark day might answer the question "What programming language should I learn?" with "None. Learn to play a musical instrument instead." Today is not a dark day, however, and I'll do my best to answer it.
The person I'm addressing this article to isn't the person that has as their objective "I want to write a Windows application" or "I want to write a GUI for Bittorrent on Linux" or "I want to write a little tool that will run on my Mac to talk to iTunes." The target of this article is someone who has a general desire to become a software developer but doesn't yet understand how to get there.
So in that context, the high level, vaguely accurate answer to the question "What programming language should I learn?" is "It really doesn't matter." Partially this is because the question is ill-formed. The specific language one uses is mostly orthogonal to developing the skills one needs to be a good software developer. Let's look at what those skills are, first, and then later we can come back to the question and make some actual recommendations, rather than just rejecting the question.
High-Level Skills
A developer needs to be able to describe a problem to be solved. She needs to be able to break the problem down into smaller, easier problems. She needs to be able to describe a set of conditions that constitute solving the problem. She needs to be able to think of tests that determine whether a given program or part of a program are correct.
Those are the sorts of skills every good developer has regardless of whether they're writing code for themselves or for the marketplace. If a developer wants to work on a project with other people, be it open source or commercial, she needs additional skills. She needs to know how to find and read documentation. She will need to know how to use an Applications Programming Interface (API) that someone else has provided. She will need to be able to know when to use an already-existing API ("almost always") versus developing a new API ("almost never"). She will need the discipline to not be constantly reinventing the wheel. She will need to know how to write documentation. She will need to understand what makes code maintainable (correct and adequate documentation, proper use of namespaces, consistent formatting, useful comments), and to actually use that knowledge when she writes code.
All of those skills apply no matter what your weapon of choice is in terms of language.
Classifying Languages
There are three rough categories of languages of interest to the modern programmer: imperative languages (sometimes you'll hear these described as procedural) such as C, C++, Java, Pascal, and Modula-3. Imperative languages are about providing a sequence of commands for the computer to execute. In functional languages such as ML, Lisp, and Scheme programs aren't so much executed as they are mathematically evaluated , as with the lambda calculus. And scripting languages such as Perl, Python, and Tcl which allow for rapid prototyping of simple tasks. Note: yes, I understand that there's no academic reason to separate scripting languages from their imperative compiled brethren, but there are practical reasons which I'll discuss later.
When programming almost any (modern, useful) language, you're going to find yourself using a variety of directives. Some will be part of the core language specification: in C, integer arithmetic and assignment will be the same on every platform. Others will be part of a library that is likely to exist on any platform your program runs on (eg, stdio in C). Lastly, there are APIs which are platform-specific; a C library routine to open a dialogue box on a Win32 OS would be an example of this.
Specific Cross-Language Skills
Learning to program skillfully is something that comes only with great time and effort. There are plenty of programs that will compile just fine and run correctly that can still be called "bad programs," in the sense that when you look at the source, it is clear that the author doesn't have a grasp on some fundamental concept. The three little pigs built houses of straw, sticks, and brick. All of them served just fine as shelter, but only the brick house was strong enough to withstand the wolf. Your goal should be to not just learn how to make your programs run, but how to be confident in their correctness, robustness, and performance, before you've written a single line of code. To achieve that state, which may seem like a paradox, you need to understand the concepts underlying the craft of programming.
A shorter way of saying this is: don't worry about learning the syntax of a language. Don't concentrate on it. Don't spend time worrying about it. Learning where the semicolons or parentheses go will come by itself, as you write code and go through compile-run-test cycles. Look that stuff up when you need to, but understand that "learning what a constructor in Java looks like" is, in the long term not a valuable thing to concentrate on. Learning what a constructor is and what it does is a valuable thing to concentrate on.
So that's what you shouldn't focus on: syntax. What should you focus on? Here, in a vague sort of didactic order, are concepts that I expect a skilled programmer to understand regardless of the language they are using -- even if the language they are using at the moment doesn't actually support the item in question.
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