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April 04, 2010

Which Programming Languages are Write-Only?

A comment on the Security Now Podcast got me thinking about the concept of write-only languages. Many times over my career, I've heard people refer to a language as write only. The implication being that no one can read the code once its written. This phrase does not refer to some magical IP technology that prevents people from stealing code you've written. It reflects the belief that the language in question is so badly designed, uses such obscure syntax, or is so powerful that any program written in the language becomes almost impenetrable to anyone trying to read the code.

I would like to humbly suggest that this concept is (mostly) nonsense. The cause of the biggest complaints seems to be unfamiliarity with the language in question. Just like most of us would find ancient Egyptian or Middle English hard to read, it can be difficult to understand a programming language if you don't know the basic syntax. Even once you learn the syntax, there is a huge difference between understanding code written in the simplest form of the language and an idiomatic program written in the language.


I have developed in Perl for a long, long time, well over a decade in fact. I have been told right to my face by fans of other languages that it is flatly impossible to write readable or maintainable code in the Perl programming language. It always comes as a shock to me, since I have written and maintained small programs and large systems in Perl for years. It would probably come as a bigger shock to the teams that worked on the Human Genome Project that used quite a bit of Perl (and were apparently able to read it). Not to mention quite a few companies that develop and run Perl code all of the time (, the BBC, TicketMaster, and cPanel all come to mind.)

When pressed, I often find that the person making this claim has never used Perl, or possibly only wrote a handful of quick scripts. This is hardly enough experience to make a reasonable judgement.


I also have quite a bit of professional experience working in C and C++. I have been told by some that these languages are also write-only. Yet, there are millions of lines of code in each of these languages running everything from embedded systems up to large research projects, financial institutions, and video processing. Obviously someone finds this code at least somewhat readable or it would not be maintained.


The comment from Steve Gibson that kicked this off involved the Forth programming language. Now, Steve is an expert at computer security and (by all accounts) an excellent programmer. But, my experience maintaining and developing a very large Forth code-base over a period of eight years, is quite different than his opinion. Forth is very different, if you are used to most modern languages. But, that does not make it write only.

I particularly find this comment amusing from someone who writes Windows software in assembler. I believe that it is possible to write readable assembler, despite not having seen many examples. But, I'm willing to bet there are many out there who would declare assembler to be the ultimate write-only language.


When I was pursuing my degree in CS, I had the opportunity to learn and program a bit in the Lisp programming language. While the syntax is not my favorite, I found well-written Lisp to be mostly readable. I've had a similar experience with the small amount of Haskell I've done. The same goes for SmallTalk and so on.

Language or Program?

While I'm not willing to suggest that a particular language is write-only, I can agree that some programs are effectively write-only. But that trait does not appear to be limited to a particular language. In every language I've worked in or even just read, I've seen examples of readable code and examples of garbage I hope to never have to maintain.

In many cases, the really bad examples come from people unfamiliar with the language or just inexperienced. The more readable code normally came from more seasoned programmers. The readable code also tended to become more readable as I became familiar with the idioms of the language or even the team that wrote the code.


Although it is probably not universally true, most of the people I have heard scream write only language have experience with only one or a few languages. Much like we Americans who only know one language and consider all of those foreign languages too hard, many of these one-language programmers are still focused on the One True Syntax and have not moved on to the concepts behind the syntax. (Forgive the stereotype, but it's a good analogy.)

In some cases, the opinion was not a case of single-language blinders, but just plain unfamiliarity.

Moving Beyond the Insults

Not everyone is going to like every programming language. That's a given. Some programming languages don't fit the way you think. But, claiming a language is write-only seems ridiculous. Most of the languages I don't like, I've programmed in long enough to be able to read them, even if I would prefer not to.

I also made an explicit decision after a discussion with another programmer years ago to have no opinion on any language I haven't used. Even if other people have really bad things to say about it. I don't know what it's like, so I have no opinion. I find this makes things easier if the job ever requires me to do a little maintenance on a language I don't know.

I've also found in the past that the languages that worked the most differently from the way I think were the most valuable to learn. Those languages were the ones that taught me the most fundamental aspects of programming, because I got to see familiar programming concepts in a completely new context.

Update: I realized that I should have made clear, that Gibson had made clear that his difficulty with reading Forth was due to unfamiliarity. He does have experience with other languages.

Posted by GWade at April 4, 2010 12:09 AM. Email comments