"Adam P. Goucher" <apgoucher@gmx.com> wrote:

Henry Baker <hbaker1@pipeline.com> wrote:

...

So what would be the single number that most computer science people would recognize and acknowledge as being representative of computer science?

Chaitin's constant represents computer science in a deep way: it embodies the eventual behaviour of every computer program.

The only problem is that its numeric value depends on your choice of prefix-free encoding of computer programs.

A bigger problem is that it is uncomputable. So even if we settled on an encoding, we wouldn't know which day to celebrate. We could celebrate June 21, the date the first stored program computer ran (in 1948). (Wow, I've been using computers for 2/3 of the time there have been computers.) Or October 30, the date the first message was sent on the ARPAnet (in 1969). Or June 23, Turing's birthday. Or June 14, Alonzo Church's birthday. Or December 26, Charles Babbage's birthday. Or November 2, George Boole's birthday. Other important constants that vary with the computer, but that at least are computable, are the largest integer that can be represented, the largest real number that can be represented, and the smallest real number greater than zero that can be represented. Or negative zero, which in some computer architectures, unlike in standard math, is distinct from positive zero. After all, the reciprocal of positive zero is positive infinity, but the reciprocal of negative zero is negative infinity. You can't get more different than that. :-) We would then celebrate computer science on the zeroth day of the zeroth month, because computer people like to count starting with zero. Or maybe on the negative zeroth day of the negative zeroth month. Or we could celebrate on the anniversary of the computer's epoch. That's January 1 (1970) for Unix, November 17 (1858) for VMS. Unix time is counted in seconds from the epoch. Instead of celebrating annually, we could celebrate when it hits some multiple of a large power of ten. Or better yet, when it hits some multiple of a large power of two. VMS time is the same, except that it isn't counted in seconds, but in microfortnights. But I think the best choice is NaN ("Not a Number"). It's unique to computer science, as it often appears in computers, but never appears on the real number line or in the complex number plane. We would celebrate on NaD ("Not a Date").