The Emperor's Old Clothes Charles Antony Richard Hoare
One-line summary: The tailor is canonized as the patron saint of all
consultants, because in spite of the enormous fees that he extracted, he was
never able to convince his clients of his dawning realization that their clothes
have no Emperor.
- Implementation design principles:
- Security - every syntactically incorrect program should be rejected by
the compiler and every syntactically correct program should give a result or
an error message that is predictable and comprehensible in terms of the
source language program itself.
violations - interpreted
languages (Perl), most programs ever written.
- Brevity - brevity of the object code produced by the compiler and
compactness of of run time working data. Implementations in which the
hardware remains much more powerful than necessary lend themselves to
simplicity, ruggedness, and reliability.
Microsoft, MacOS, Netscape 3.0
- Clean, tight, procedural interfaces - entry and exit conventions for
procedures and functions should be as compact and efficient as for tightly
coded machine-code subroutines.
violations - termios/ioctl,
- The compiler should use only a single pass.
I, being completely
naiive about compilers, dare to disagree.
- Language features:
- Programming notations must be designed to maximize the number of errors
which cannot be made, or if made, can be reliably detected at compile time.
The way to shorten programs is to use procedures, not to omit vital
violations - Perl, assembly
- Programmers are surrounded by complexity. Programs are complex, because
of the large number of comflicting objectives for each of our programming
projects. If our basic tool, the langauge in which we design and code our
programs, is also complicated, the language itself becomes part of the
problem rather than part of its solution.
violations - Perl,
- The programmer should make a number of definite assertions which can be
checked individually, and from which the correctness of the whole program
violations - link-layer protocols, TCP backoff
algorithms, UNIX process scheduling
- A feature which is omitted can always be added later, when its design
and its implications are well understood. A feature which is included before
it is fully understood can never be removed later.
- x86, Perl
- Second System Syndrome:
- Elliott 503 Mark II software project had failed, ostensibly due to
hardware limitations. [They] were fortunate that hardware limitations had
protected them from the arbitrary excesses of [their] software designs.
violations - Win95, Multics, Word vs. Bank Street Writer
- A lack of clarity in specification is one of the surest signs of a
deficiency in the program it describes, and the two faults must be removed
simultaneously before the project is embarked upon.
- most committee designs (ANSI, ITU, OSI, MPEG)
- You shouldn't trust us intelligent programmers. We can think up such
good arguments for convincing ourselves and each other of the utterly
violations - Java
- There are two ways of constructing a software design: One way is to make
it so simple that there are obviously no deficiencies and the other way is
to make it so complicated that there are no obvious deficiencies. The
price of reliability is the pursuit of the utmost simplicity.
violations - Multics!
RelevanceThe next rocket to go astray as a result of programming
language error may not be an exploratory space rocket on a harmless trip to
Venus: It may be a nuclear warhead exploding over one of our own cities.
- Perl violates nearly every principle put forward in this paper. Why, then,
is it so popular, powerful, and responsible for so much success? I think it
is due to the discipline and organization of the programmers that complements
the flexibility of the langauge, rather than the structure and elegance of
- Microsoft violates nearly every principle put forward in this paper. Why,
then, is it so popular, powerful, and responsible for so much success? I
think it is due to the power of monopoly, the manipulation of capatilistic
forces, and the allure of the dark side of the force.
- NeXT obeys nearly every principle put forward in this paper. Why, then, is
it so unpopular, powerless, and responsible for so little success?
Engineers, no matter how intelligent, do not run corporations and do not
sway market forces.