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I have a message:
x2400\x1100\x2001\x1020\x2100\x0900\x2008\x2012\x0900\x1001\x2001\x1010\x2001\x0900\x0802\x0812\x1200\x2010\x0802\x1004\x0820\x1010\x2100\x2002\x1012
It's in IBM column binary format. I have read some documentation, but I can't do by myself.
Rather than "do your homework for you", I'll provide a table giving the full character set in IBM 360 column-binary format. You can then look up each character in the table to decode the meaning of any message, not just this one.
& 2000
- 1000
0 0800
1 0400
2 0200
3 0100
4 0020
5 0010
6 0008
7 0004
8 0002
9 0001
A 2400 J 1400 / 0C00
B 2200 K 1200 S 0A00
C 2100 L 1100 T 0900
D 2020 M 1020 U 0820
E 2010 N 1010 V 0810
F 2008 O 1008 W 0808
G 2004 P 1004 X 0804
H 2002 Q 1002 Y 0802
I 2001 R 1001 Z 0801
¢ 2202 ! 1202 : 0202
. 2102 $ 1102 , 0902 # 0102
< 2022 * 1022 % 0822 @ 0022
( 2012 ) 1012 _ 0812 ' 0012
+ 200A ; 100A > 080A = 000A
| 2006 ¬ 1006 ? 0806 " 0006
The column-binary code is constructed as two groups of six bits, so that holes punched in the Y and X "zone" rows appear as set bits in the first digit; rows 0-3 go in the second digit, rows 4 and 5 go in the third digit, and rows 6-9 go in the fourth digit.
The characters themselves are clearly divided into three categories. The first category is a single punch, which is used mainly for numbers. The second category is a two-punch combination, where one of the punches is an X, Y, or 0 "zone" punch, which is mainly used for letters. The third category uses the 2 row as an additional "zone", and may use 2 or 3 punches, to provide various punctuation characters.
In addition, you may encounter columns with no punches which read as spaces, and columns with all holes punched, which is an erased character.
I have a message. It's in IBM column binary format.
To start it's important to keep in mind that Punch cards are not a binary format, but an n out of 12 encoding with n being 1 to 4. So a column can have one to four holes (*1). The columns are named (top down) 12, 11 (*3), 0, 1, 2, 3, 4, 5, 6, 7, 8, 9.
Column Binary Format is a way to store a perfect image of a punch card ordered by columns. 12 possible positions need 12 bit, so more what fits a byte, thus two bytes are needed. To make it as easy manageable as possible the 12 positions get split into two groups of six (*2) simply from top to bottom and left to right. Or in other word, the positions of a column (character) get spread like this:
Column 12, 11, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9
Byte 1 1 1 1 1 1 2 2 2 2 2 2
Bit (2^n) 5 4 3 2 1 0 5 4 3 2 1 0
So x'1100' (or xx010001.xx000000) simply denotes two holes in position 11 and 2. If my memory serves me well, that would be the letter L.
Norbert's keypunch site already includes much information. Just scroll down. In fact, it not only explains what is written here in way better way, it can as well be used to decode.
Binary Mode By Manual Input: Press the “BINARY” key on the visual keyboard or use TAB + SHIFT on a real keyboard. Enter a 4-digits hexadecimal number for the pattern to be punched and confirm the dialog either by hitting “Enter” or by pressing the button “Enter”. Please mind that only valid hexdecimal numbers are accepted, the Virtual Keypunch will issue a “bing” otherwise.
Just go ahead and use it.
Or use the table Chromatix was so kind to provide.
*1 - Well, four is rather rare and three only used for additional punctuations.
*2 - Giving a monotone sequence of 64 encodings
*3 - The odd sequence comes from history, as the top rows are a later extension.
