There is a real difference between the two models. Open source gives you a lot more control. When you're using open source software and you want to understand what it's doing, you can read the source code and find out. If you want, you can even change the software and recompile it.
One reason you might want to do that is to fix a bug. You can't fix bugs in Microsoft Windows, for example, because you don't have the source code. (In theory you could hack the object code, but in practice this is very hard. It's also probably forbidden by the license agreement.) This can be a real problem. When a new security hole is discovered in Windows, you have to wait for Microsoft to release a fix. And security holes at least get fixed fast. If the bug merely paralyzes your computer occasionally, you may have to wait till the next full release for it to be fixed.
But the advantage of open source isn't just that you can fix it when you need to. It's that everyone can. Open source software is like a paper that has been subject to peer review. Lots of smart people have examined the source code of open source operating systems like Linux and FreeBSD and have already found most of the bugs. Whereas Windows is only as reliable as big-company QA can make it.
Open source advocates are sometimes seen as wackos who are against the idea of property in general. A few are. But I'm certainly not against the idea of property, and yet I would be very reluctant to install software I didn't have the source code for. The average end user may not need the source code of their word processor, but when you really need reliability, there are solid engineering reasons for insisting on open source.
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 Perlor 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.