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IBM 7090/94 Character Representation
The 7090/94 used six-bit representations for characters for a total of 64 possible characters -- the BCD character set. However, only 51 were commonly used:
BCD Character Set
| Character | BCD (Binary/Octal) | | Character | BCD (Binary/Octal) | | Character | BCD (Binary/Octal) |
|---|
| '0' | 000000/00 | | 'E' | 010101/25 | | 'R' | 101001/51 |
|---|
| '1' | 000001/01 | | 'F' | 010110/26 | | [Special-2] | 101010/52 |
|---|
| '2' | 000010/02 | | 'G' | 010111/27 | | '' | 101011/53 |
|---|
| '3' | 000011/03 | | 'H' | 011000/30 | | '*' | 101100/54 |
|---|
| '4' | 000100/04 | | 'I' | 011001/31 | | ' ' (Blank) | 110000/60 |
|---|
| '5' | 000101/05 | | [Special-1] | 011010/32 | | '/' | 110001/61 |
|---|
| '6' | 000110/06 | | '.' | 011011/33 | | 'S' | 110010/62 |
|---|
| '7' | 000111/07 | | ')' | 011100/34 | | 'T' | 110011/63 |
|---|
| '8' | 001000/10 | | '-' | 100000/40 | | 'U' | 110100/64 |
|---|
| '9' | 001001/11 | | 'J' | 100001/41 | | 'V' | 110101/65 |
|---|
| '=' | 001011/13 | | 'K' | 100010/42 | | 'W' | 110110/66 |
|---|
| ' " ' (Double Quote) | 001100/14 | | 'L' | 100011/43 | | 'X' | 110111/67 |
|---|
| '+' | 010000/20 | | 'M' | 100100/44 | | 'Y' | 111000/70 |
|---|
| 'A' | 010001/21 | | 'N' | 100101/45 | | 'Z' | 111001/71 |
|---|
| 'B' | 010010/22 | | 'O' | 100110/46 | | '±' | 111010/72 |
|---|
| 'C' | 010011/23 | | 'P' | 100111/47 | | ',' | 111011/73 |
|---|
| 'D' | 010100/24 | | 'Q' | 101000/50 | | '(' | 111100/74 |
|---|
The [Special-1] character was, apparently, a "+/0" character and [Special-2] was, apparently, an 'O' with a horizontal bar across the top. The characters read by the card reader were defined by the plug-board programming on the IBM 711 card reader and could vary slightly from site to site.
With six-bit characters, each 36-bit word of memory could hold up to six characters. The six-character string "MOTHER" would be represented in a 36-word of memory as the binary string:
100100100110110011011000010101101001
or, in octal, as:
O444663302551
Source code (and data) were usually loaded into the 7090/94 from 80-column punched cards (typically indirect through magnetic tape). The paper cards usually could contain up to 80 characters of information in a horizontal line with each character containing data in 12 vertical positions.
Counting, in a single character position of 12 vertical positions, from the top to the bottom of the card, the positions were denoted as 12-punch, 11-punch, 0-punch, 1-punch, 2-punch,... 9-punch as follows:
The code that was used to read characters from cards was as follows:
- 12-Punch and 1-Punch together in a column: 'A', 12-2: 'B', 12-3: 'C', 12-4: 'D', 12-5: 'E', 12-6: 'F', 12-7: 'G', 12-8: 'H', 12-9: 'I'
- 11-Punch and 1-Punch together in a column: 'J', 11-2: 'K', 11-3: 'L', 11-4: 'M', 11-5: 'N', 11-6: 'O', 11-7: 'P', 11-8: 'Q', 11-9: 'R'
- 0-Punch and 2-Punch together in a column: 'S', 0-3: 'T', 0-4: 'U', 0-5: 'V', 0-6: 'W', 0-7: 'X', 0-8: 'Y', 0-9: 'Z'
- For numeric '1' through '9', punch only the number omitting all three of the top columns (12-Punch, 11-Punch, 0-Punch)
- Special Characters (e.g., comma, period, etc.) required special groupings of punches
http://www.frobenius.com/characters.htm -- Last Revision: 23 August 2001
Copyright © 1996 - 2017 Jack Harper (unless otherwise noted)
