[GreenKeys] Punchcards. Was: off topic? sort of..

[Jones, Douglas W]

On Sep 10, 2015, at 10:09 AM, Jim Haynes wrote:

> Then there were the Remington Rand - Univac punch cards which had round
> holds and 45 columns and 12 rows treated as 90 columns of 6 rows each.

Prior to 1928, IBM also used 45 column 12 row round hole cards.  In 1928, they announced a new standard card layout supported by their new line of punches and tabulating machines.  The new line had two major features:

a) 80 columns of data per card, and

b) An alphanumeric code that allowed upper case letters (and a very sparse set of punctuation) in addition to the numbers.

Numerals were punched with a single hole per column. + and - were also single hole punches (in the top two rows, numbered 11 and 12).

Letters were punched with two punches in a column, one punch in rows 10, 11 and 12, and a second punch in rows 1 through 9.  That allowed coding 9 x 3 = 27 distinct symbols, usually interpreted as 26 upper case letters plus the / character.

Later, more advanced coding schemes included support for more punctuation with 3 punches per column (in these codes, row 8 was always punched, and there was a fairly natural conversion from the card codes to a 6-bit code, which is why the coding scheme is known as BCD.

All this is documented on my punched-card codes web page:
-- http://homepage.cs.uiowa.edu/~jones/cards/codes.html

		Doug Jones
		jones at cs.uiowa.edu