So, these crazy little punch card guys- not that complicated IF you have a chart to decode them with. So, basically the card has columns of the digits 0-9. And there are also two places to punch above those two that count as "11" and "12". Eleven is the lower one, and twelve is the top-most punch area.
So, here is sot of the basic code for how to form letters and numbers on the punch card:
To type the number 0, punch out 0
To type the number 1, punch out 1
etc.
0-9 stand only for numbers.
If 11 is punched, it is -
If 12 is punched, it is *
If 0, 11 or 12 are punched in combination with one of the other digits, it is a letter.
For example, the letter A is formed by punching out 12 and 1 in the same column
B is formed by 12 and 2
C= 12 and 3
D= 12 and 4
etc
I= 12 and 9
J= 11 and 1
K=11 and 2
etc
R= 11 and 9
Here's a wierd one- 0 and 1 punched together means /
Then, S= 0 and 2
all the way to the end, Z= 0 and 9
Some other special characters are formed by combining punches. For example, when 12, 3, and 8 are all punched on the same column, that is a period. When 11, 4, and 8 are all punched on the same column that means *.
This is a good picture of a punch card where the answer to the punches is written at the top, so you can see if you got it right once you decode it.
If you want to read a really confusing explanation go here! http://en.wikipedia.org/wiki/Punch_card#IBM_80_column_punch_card_format
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