The Universe of Discourse

My 1992 view of the problems of computer programming in 1992

While cleaning out my office today, I found this, which I wrote in 1992:

In the middle 1970's, the IBM corporation did (and perhaps still does) most of their in-house programming in a computer language called FORTRAN. They had a pretty good FORTRAN compiler, called the FORTRAN G compiler. It was fast at translating FORTRAN into machine instructions, and the machine instructions it produced implemented the desired behavior fairly efficiently. Nevertheless, IBM decided to write a new compiler.

This was very daring in the middle 1970's, because compilers were quite complicated programs, and are difficult to write, and it was surprising that IBM was willing to invest the vast resources that a new compiler would require when an adequate compiler was still available. IBM spent millions of dollars and hundreds of programmer-years, and produced the FORTRAN H compiler, which was fast, efficient, and full of nice features. It was an excellent compiler and is still the one that they use.

Here is the first punch line: Compiler programs are no longer difficult to write. The past fifteen years have seen an enormous increase in our understanding of compiler technology and how to write a compiler. Compilers are so easy to write now that third-year undergraduate computer science majors are expected to be able to turn out passable compilers in one semester.

Now a question: Since we're obviously thousands of times better at producing compilers than we were fifteen years ago, so much so that a single undergraduate can write a passable one in four months, why hasn't IBM invested millions of dollars and hundreds of programmer-years to produce a super FORTRAN I compiler that's thousands of times better than the FORTRAN H compiler?

The answer is that compiler program quality is no longer the limiting factor on our ability to write computer programs. The problems that programmers face no longer have to do with how good the compiler is. Instead, they are problems of method and language. We don't really know how to program yet, or how to manage our programs. We don't really know what we want to say or how to say it. We don't have good computer languages for expressing what we want to computer to do. We don't know how to think about programming. In short, the reason IBM doesn't bother with a super FORTRAN I compiler, is that no matter how good it was, it would still be FORTRAN.

Computer programming is still a black art. It's less than fifty years old, and nobody is very good at it yet. We can make better tools than we know how to use.

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