För några dagar sedan skrev jag ett inlägg om anledningen till att det är just 80 tecken på en kommandorad. Anledningen var att de gamla hålkorten hade just 80 kolumner. Men då ställer de vetgiriga den naturliga följdfrågan: Varför var det just 80 kolumner på ett håkort?
Här kommer ett svar som jag har hittat på nätet:
As to 'why punch cards were 80 columns', the answer is probably
similar to "why railroad tracks are 4' 8-1/2" apart." Standard
lettering for a _lot_ of business applications is 10 characters/inch.
A punch-card is 8-1/2" wide. between the cut corner, and the rounded
edge, you have just over 8" available for the printing on the top.
0.1" spacing was also a common unit for a lot of kinds of
electro-mechanical production. I suspect that 'ease of manufacture'
to that unit of measure played into the decision.
80 cols was *not* universal, though. Burroughs used a 96-column card,
that was less than 1/2 the size, side-to-side, of the Hollerith card.
They would _completely_ fit in a shirt-pocket.
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Also, the size of the punch card was based on the size of US currency
at the time, which was larger than is now. Punched cards for
information processing were invented by Herman Hollerith in 1890 and
his outfit eventually was purchased by the C-T-R company which evolved
into IBM in the early 1900s. The early company hired Thomas J. Watsor
Sr to be its manager. He was not the "founder" of IBM, though he took
the ragtag little outfit and turned into a worldwide organization.
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Här är för övrigt två bilder på några av de äldsta kortstansar och kortläsare som finns. De tog jag igår på National Museum of American History:s utställning Information Age: People, Information & Society.
Där ser man! Nu är t.om jag nöjd med förklaringen. =)
Posted by: Lars Olofsson | 2004-10-05 at 02.47