Punch Card Encoding - griffingilreath/Punch-Card-Project GitHub Wiki
IBM Punch Card Encoding Reference
This document provides a comprehensive reference for IBM punch card character encoding systems, based on historical documentation and research.
IBM 80-Column Punch Card Format
Physical Specifications
| Feature | Specification |
|---|---|
| Dimensions | 7β Γ 3ΒΌ inches (187mm Γ 82.5mm) |
| Thickness | ~0.007 inches |
| Hole Shape | Rectangular (~1mm Γ 3mm) |
| Column Count | 80 (numbered 1-80 left to right) |
| Row Count | 12 (12, 11, 0-9 from top to bottom) |
| Corner Cut | Upper-left corner (for orientation) |
| Horizontal Pitch | ~0.087 inches (~2.21 mm) |
| Vertical Pitch | ~0.25 inches between rows |
Card Layout Visualization
1 2 3 4 5 6 7 8
012345678901234567890123456789012345678901234567890123456789012345678901234567890
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12 | |
11 | |
0 | |
1 | |
2 | |
3 | |
4 | |
5 | |
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8 | |
9 | |
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Character Encoding Systems
IBM punch cards used specific hole patterns (or "punches") to represent characters. Different character sets were used depending on the application, but the physical encoding remained consistent.
Encoding Notation
Punch patterns are typically written using row numbers separated by hyphens. For example:
12-1means holes in rows 12 and 10-2-8means holes in rows 0, 2, and 8
Zone and Digit Punches
- Zone punches: Rows 12, 11, and 0
- Numeric punches: Rows 1 through 9
IBM 026 Keypunch (FORTRAN) Character Set
Used primarily for scientific applications and FORTRAN programming.
| Character | Punch Pattern | Description |
|---|---|---|
| A | 12-1 | Letter A |
| B | 12-2 | Letter B |
| C | 12-3 | Letter C |
| D | 12-4 | Letter D |
| E | 12-5 | Letter E |
| F | 12-6 | Letter F |
| G | 12-7 | Letter G |
| H | 12-8 | Letter H |
| I | 12-9 | Letter I |
| J | 11-1 | Letter J |
| K | 11-2 | Letter K |
| L | 11-3 | Letter L |
| M | 11-4 | Letter M |
| N | 11-5 | Letter N |
| O | 11-6 | Letter O |
| P | 11-7 | Letter P |
| Q | 11-8 | Letter Q |
| R | 11-9 | Letter R |
| S | 0-2 | Letter S |
| T | 0-3 | Letter T |
| U | 0-4 | Letter U |
| V | 0-5 | Letter V |
| W | 0-6 | Letter W |
| X | 0-7 | Letter X |
| Y | 0-8 | Letter Y |
| Z | 0-9 | Letter Z |
| 0 | 0 | Digit 0 |
| 1 | 1 | Digit 1 |
| 2 | 2 | Digit 2 |
| 3 | 3 | Digit 3 |
| 4 | 4 | Digit 4 |
| 5 | 5 | Digit 5 |
| 6 | 6 | Digit 6 |
| 7 | 7 | Digit 7 |
| 8 | 8 | Digit 8 |
| 9 | 9 | Digit 9 |
| + | 12 | Plus sign |
| - | 11 | Minus sign |
| * | 11-8-4 | Asterisk |
| / | 0-1 | Slash |
| = | 0-8-3 | Equal sign |
| . | 12-8-3 | Period |
| , | 0-8-3 | Comma |
| $ | 11-8-3 | Dollar sign |
| ( | 12-8-5 | Open parenthesis |
| ) | 11-8-5 | Close parenthesis |
| blank | No punch | Space character |
IBM 029 Keypunch (Commercial/Symbolic) Character Set
Expanded character set for business applications, assembly language, and other uses.
| Character | Punch Pattern | Description |
|---|---|---|
| # | 8-3 | Number sign |
| @ | 8-4 | At sign |
| % | 0-8-4 | Percent sign |
| & | 12 | Ampersand |
| ! | 11-8-7 | Exclamation mark |
| ? | 0-8-7 | Question mark |
| " | 8-7 | Quotation mark |
| ' | 8-5 | Apostrophe |
| : | 8-2 | Colon |
| ; | 11-8-6 | Semicolon |
| < | 12-8-6 | Less than |
| > | 0-8-6 | Greater than |
| [ | 12-8-2 | Open bracket |
| ] | 11-8-2 | Close bracket |
| { | 12-0 | Open brace |
| } | 11-0 | Close brace |
Note: The Commercial/Symbolic set includes all the characters from the FORTRAN set, with some different assignments.
EBCDIC (Extended Binary Coded Decimal Interchange Code)
Introduced with the IBM System/360 in 1964, EBCDIC is an 8-bit character encoding system that mapped punch card codes to computer memory.
EBCDIC Encoding Pattern
EBCDIC used the following bit positions to represent punch card holes:
- Bit 0 = 12 punch
- Bit 1 = 11 punch
- Bit 2 = 0 punch
- Bit 3 = 1 punch
- Bit 4 = 2 punch
- Bit 5 = 3 punch
- Bit 6 = 4 punch
- Bit 7 = 5 punch
- Bit 8 = 6 punch
- Bit 9 = 7 punch
- Bit 10 = 8 punch
- Bit 11 = 9 punch
ASCII Punch Card Extension (ANSI X3.26-1970)
In 1970, the American National Standards Institute published ANSI X3.26, which defined punch combinations for all 128 ASCII characters on a 12-row card.
Lowercase Letter Encoding
| Character | Punch Pattern | Description |
|---|---|---|
| a | 12-0-1 | Lowercase a |
| b | 12-0-2 | Lowercase b |
| c | 12-0-3 | Lowercase c |
| d | 12-0-4 | Lowercase d |
| e | 12-0-5 | Lowercase e |
| f | 12-0-6 | Lowercase f |
| g | 12-0-7 | Lowercase g |
| h | 12-0-8 | Lowercase h |
| i | 12-0-9 | Lowercase i |
| j | 12-11-1 | Lowercase j |
| k | 12-11-2 | Lowercase k |
| l | 12-11-3 | Lowercase l |
| m | 12-11-4 | Lowercase m |
| n | 12-11-5 | Lowercase n |
| o | 12-11-6 | Lowercase o |
| p | 12-11-7 | Lowercase p |
| q | 12-11-8 | Lowercase q |
| r | 12-11-9 | Lowercase r |
| s | 11-0-2 | Lowercase s |
| t | 11-0-3 | Lowercase t |
| u | 11-0-4 | Lowercase u |
| v | 11-0-5 | Lowercase v |
| w | 11-0-6 | Lowercase w |
| x | 11-0-7 | Lowercase x |
| y | 11-0-8 | Lowercase y |
| z | 11-0-9 | Lowercase z |
Punch Card Usage Conventions
FORTRAN Coding Sheets
FORTRAN punch cards typically followed a specific column layout:
| Columns | Purpose |
|---|---|
| 1-5 | Statement number |
| 6 | Continuation indicator |
| 7-72 | FORTRAN statement |
| 73-80 | Sequence number |
COBOL Coding Sheets
COBOL programs used a different column layout:
| Columns | Purpose |
|---|---|
| 1-6 | Sequence number |
| 7 | Indicator area |
| 8-11 | Area A (divisions, sections, paragraphs) |
| 12-72 | Area B (statements) |
| 73-80 | Identification |
Historical Significance
The phrase "Do not fold, spindle, or mutilate" originated as a warning printed on punch cards but became a cultural meme in the 1960s, symbolizing resistance to dehumanization by bureaucracy and computer systems.
References
- IBM Documentation: "IBM Punched Card Stock Specification"
- Columbia University Computing History Archive
- University of Iowa Punch Card Collection (D. Jones)
- ANSI X3.26-1970: Hollerith Punched Card Code
- "Two-Bit History: The Punched Card Tabulator"
- "The Craft of Coding: Understanding Historical Computing"