Most programmers, most of the time, program in high-level languages. Few use assembly language now. Computer time has become much cheaper, while programmer time is as expensive as ever, so it's rarely worth the trouble of writing programs in assembly language. You might do it in a few critical parts of, say, a computer game, where you wanted to micromanage the hardware to squeeze out that last increment of speed.

Fortran, Lisp, Cobol, Basic, C, Pascal, Smalltalk, C++, Java, Perl, and Python are all high-level languages. Those are just some of the better known ones. There are literally hundreds of different high-level languages. And unlike machine languages, which all offer similar instruction sets, these high-level languages give you quite different concepts to build programs out of.

So which one do you use? Ah, well, there is a great deal of disagreement about that. Part of the problem is that if you use a language for long enough, you start to think in it. So any language that's substantially different feels terribly awkward, even if there's nothing intrinsically wrong with it. Inexperienced programmers' judgements about the relative merits of programming languages are often skewed by this effect.

Other hackers, perhaps from a desire to seem sophisticated, will tell you that all languages are basically the same. I've programmed in all kinds of languages, said the tough old hacker as he eased up to the bar, and it don't matter which you use. What matters is whether you have the right stuff. Or something along those lines.

This is nonsense, of course. There is a world of difference between, say, Fortran I and the latest version of Perl—or for that matter between early versions of Perl and the latest version of Perl. But the tough old hacker may himself believe what he's saying. It's possible to write the same primitive Pascal-like programs in almost every language. If you only ever eat at McDonald's, it will seem that food is much the same in every country.

Some hackers prefer the language they're used to, and dislike anything else. Others say that all languages are the same. The truth is somewhere between these two extremes. Languages do differ, but it's hard to say for certain which are best. The field is still evolving.

10.5. Abstractness

Just as high-level languages are more abstract than assembly language, some high-level languages are more abstract than others. For example, C is quite lowlevel, almost a portable assembly language, whereas Lisp is very high-level.

If high-level languages are better to program in than assembly language, then you might expect that the higher-level the language, the better. Ordinarily, yes, but not always. A language can be very abstract, but offer the wrong abstractions. I think this happens in Prolog, for example. It has fabulously powerful abstractions for solving about 2% of problems, and the rest of the time you're bending over backward to misuse these abstractions to write de facto Pascal programs.

Another reason you might want to use a lower-level language is efficiency. If you need code to be super fast, it's better to stay close to the machine. Most operating systems are written in C, and it is not a coincidence. As hardware gets faster, there is less pressure to write applications in languages as low-level as C, but everyone still seems to want operating systems to be as fast as possible. (Or maybe they want the prospect of buffer-overflow attacks to keep them on their toes.)

The biggest debate in language design is probably the one between Those who think that a language should prevent programmers from doing stupid things, and those who think programmers should be allowed to do whatever they want. Java is in the former camp, and Perl in the latter. (Not surprisingly, the DoD is big on Java.)

Partisans of permissive languages ridicule the other sort as "B&D" (bondage and discipline) languages, with the rather impudent implication that those who like to program in them are bottoms. I don't know what the other side call languages like Perl. Perhaps they are not the sort of people to make up amusing names for the opposition.

The debate resolves into several smaller ones, because there are several ways to prevent programmers from doing stupid things. One of the more active questions at the moment is static versus dynamic typing . In a statically-typed language, you have to know the kind of values each variable can have at the time you write the program. With dynamic typing, you can set any variable to any value, whenever you want.

Advocates of static typing argue that it helps to prevent bugs and helps compilers to generate fast code (both true). Advocates of dynamic typing argue that static typing restricts what programs you can write (also true). I prefer dynamic typing. I hate a language that tells me what to do. But some smart people seem to like static typing, so the question must still be an open one.

Another big topic at the moment is object-oriented programming. It means a different way of organizing programs. Suppose you want to write a program to find the areas of two-dimensional figures. At first it only has to know about circles and squares. One way to do it would be to write a single piece of code, within which you test whether you're being asked about a circle or a square, and then use the corresponding formula to find the area. The object-oriented way to write this program would be to create two classes , circle and square, and then attach to each class a snippet of code (called a method ) for finding the area of that type of figure. When you need to find the area of something, you ask what its class is, retrieve the corresponding method, and run that to get the answer.

These two cases may sound very similar, and indeed what actually happens when you run the code is much the same. (Not surprisingly, since you're solving the same problem.) But the code can end up looking quite different. In the object-oriented version, the code for finding the areas of squares and circles may even end up in different files, one part in the file containing all the stuff to do with circles, and the other in the file containing the stuff to do with squares.

The advantage of the object-oriented approach is that if you want to change the program to find the area of, say, triangles, you just add another chunk of code for them, and you don't even have to look at the rest. The disadvantage, critics would counter, is that adding things without looking at what was already there tends to produce the same results in programs that it does in buildings.

The debate about object-oriented programming is not as clear-cut as the one about static versus dynamic typing. With typing you have to choose one or the other. But the object-orientedness of a language is a matter of degree. Indeed, there are two senses of object-oriented: some languages are object-oriented in the sense that they let you program in that style, and others in the sense that they force you to.

I see little advantage in the latter. Surely a language that lets you do x is at least as good as one that forces you to. So as regards languages , at least, we can finesse this question. Sure, use a language that lets you write object-oriented programs. Whether you ever actually want to then becomes a separate question.

10.8. Renaissance

One thing I think everyone in the language business will agree on is that there are a lot of new programming languages lately. Until the 1980s, only institutions could afford the hardware needed to develop programming languages, and so most were designed by professors or researchers at large companies. Now a high school kid can afford all the hardware necessary.