11 Jan
1999
11 Jan
'99
6:59 a.m.
>Once databases started being kept on disk drives,
saving two bytes for each
>date may not have sounded like much, but it literally did save money. It
>takes fewer disk packs (and perhaps fewer drives) to store 92-byte records
>than 94-byte records. I don't know how many decisions were made on that
>basis, but you can't realistically ignore it.
There's a dozen lame excuses as to why They Did It
That Way. Few of
them make any sense. If they'd stored the year in a seven or eight
bits offset from their earliest year, instead of two ASCII or BCD
digits, they'd halve their storage requirements.
Lame excuse ?
Sorry, but there is a _big_ difference. Stored as (unsigned) BCD,
I can convert a date in just two machine instructions (UNPK and OI)
- not only the year but the whole date and maybe even time - but if
I use a binary year, I need at least 5 instructions (XR, IC, CVD,
UNPK, OI) just for the year (not to mention 8 additional bytes
of scrap mem :) - and, at least in our case, time was more important.
We had to serve up to 300 users on a 0.8 MIPS CPU (Average of 4
transactions per second) in 1980. So, instruction counting was a
serious business (and it still is !). Of course The space was also
limited, when the biggest disk available was just 144 MB - and in fact,
althrough instruction count isn't that important anymore, space still
is - If you have life data bases of more than 20 million entries, hundred
bytes more or less is just another disk drive .)
At least for this project we are finished since more than half a
year with all Y2K changes - did anybody say Europe is late ? Doing
a job is (in most cases) a silent thing and don't need any morning
and ranting about the upcomming doom - Lets wait and see.
Gruss
H.
P.S.: And for the Russian thing (Zane), there is no real difference
between a still in use PDP11 in the US, Germany or Russia - in fact,
I trust some russian military technology a more than US or German.
Tricks are alway better than transistors (Glenn Henry).
--
Ich denke, also bin ich, also gut
HRK