h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Hi Jim, after reading a guide article about a basic checksum
A24830831 and speculation on the method used for the guide entry number system, i had a little chat with the author who suggested asking you. I feel slightly silly now for i dont know maybe there isnt such a thing and its all a total fabrication; but it is quite interesting nontheless and i am interested to find out.

Sorry for not replying sooner - I've been working in a different part of the BBC for a few months, and haven't been paying attention to my messages.

The checksum for articles is very simple. It's the last digit and you calculate it as follows:

Add up the digits of the actual ID.
The checksum is the number which would need to be added to the checksum to make it end in a 9.

For example, take article A44342598

The actual database ID is 4434259

4+4+3+4+2+5+9 = 31
number required to make the checksum end in 9: 8 (31+8=39)

so the check digit is 8 (as seen in the full h2g2ID).

Hi Jim

No problem, i was in no hurry for the answer. Actually, it was something i came across, which another researcher had posted; and i actually figured it out(somehow), which i am happy about.

All very interesting Jim, and i have another question: how come we have no entry 42?

There can't be an article 42 because that has an incorrect checksum. However, Article A423 is the article with the actual ID 42. Nothing very special.

We saved that for User U42.

Yea thats as it should be i think.

I feel a slight fraud for i have never actually read anything by DNA, i stumbled upon the guide, quite by chance: wish i could be as lucky in everything i do.



Thanks for getting back to me. Douglas Adams seems to have been a gentleman: and so are you!