Emulated Punched Card Decks

Part of the Punched Card Collection
by Douglas W. Jones
THE UNIVERSITY OF IOWA Department of Computer Science

The purpose of this file is to document the card formats I hope will be used by developers of emulators for antique computers, so that card "decks" punched on one emulator will be readable by others, and so that a standard suite of utility software can be used to support "card" processing on all such emulators.

The following file format is proposed for use on such emulators:

One column of a card holds 12 bits; in the file, we lay them out as follows, with ones representing punched holes:

      Top                  Bottom
        _ _ _ _ _ _ _ _ _ _ _ _
      12 11 0 1 2 3 4 5 6 7 8 9
       |     |                 |
       |Zone |     Numeric     |
Note that there are multiple mappings from ASCII to card codes, reflecting different keypunches and reflecting different interpretations of non-ASCII graphics such as cent-sign and logical-not.

A design dilemma presents itself: There are two rational ways to map card columns to byte sequences, highbyter (or bigendian) and lowbyter (or littleendian). The choice is arbitrary. Here, we will be bigendian as follows:

               column 1                column 2
       |_ _ _ _ _ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _ _ _ _ _|
       |               |               |               |
             byte 1          byte 2          byte 3
Card files need a distinguished magic number or prefix to prevent accidental interpretation of random files as virtual card decks. Here, we will use the ASCII prefix "H80", in honor of the FORTRAN Hollerith format used to read one card image as uninterpreted text.

This prefix allows extension to H82, where both columns 0 and 81 are represented -- note that some verifiers punched in column 0, and that IBM 026 keypunches could generally punch column 81. Emulators should generally accept H82 files and ignore the extra leading and trailing columns! Similarly H51 can be used to represent the 51 column cards used for some business forms, and H53 can be used to represent these cards with data punched in columns 0 or 52. Mixing multiple card sizes in one deck was never practical, so emulators need not support it, and most emulators need only support H80 (and H82, but ignoring columns 0 and 81).

To support keypunch emulators and card deck display and editing programs, a 3 byte prefix is needed on each card. Emulators that read the holes on a card should ignore this prefix (other than using it to verify that a card-file is indeed being read). The prefix format is as follows:

             byte 1          byte 2         byte 3
       |_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _|_ _ _ _ _ _ _ _|
       | | Color | |cut| | |     |form | |    logo     |
                  |       |   |
                corner    | punch
Cards came in many colors, and cream cards (the default) came with pale colored stripes coarsely printed across the top margin. The following color selection should be more than sufficient:
      Color:  cream (unbleached)      0000 default!
              white                   0001
              yellow                  0010
              pink                    0011
              pale blue               0100
              pale green              0101
              pale orange             0110
              pale brown              0111 rare
              yellow stripe           1010 very common!
              pink stripe             1011
              pale-blue stripe        1100
              pale-green stripe       1101
              pale-orange stripe      1110
              pale-brown stripe       1111
Most cards had rounded corners to prevent fraying, but you could save a bit of money by ordering square cornered cards. One of the top corners of each card was usually cut off diagonally. Cards with no cut and with both top corners cut were made!
      Corner: round   0  default
              square  1

      Cut:    neither 00 rare
              right   01 common
              left    10 default
              both    11 rarest
Keypunches usually printed on the top edge of the card as they punched. Each model of keypunch printed its own interpretation of the character codes used, and if a card was punched by a high speed computer-driven punch, it was not usually printed. Any deck of cards could be run through an interpreter which overprinted the card with a somewhat eccentric interpretation of the data on the card. Accurate emulation of the particular character sets used by different interpreters is probably not necessary (most programmers got used to the fact that interpreters hardly ever printed in the character set that they wanted!)
      Interp: no      0  default
              yes     1

      Punch:  none            000 punch didn't print
              026 Commercial  001 older, with "&-#@.¤$*,%"
              026 FORTRAN     010 older, with "+-='.)$*,("
              029             100 default
Cards could be printed with a number of forms and logos. Most corporate logo cards were based on a standard form, with the logo added in light grey in the center of the card. The set of available forms was open ended, and of course, the set of logos was open ended. This virtual card format allows only a few of them (and far too many logos).
      Forms:  no printing  000
              IBM 5081     001 all numeric rows marked (default)
              IBM 507536   010 only colmns 1, 80 and row 0 marked
              IBM 5280     011 8 fields, 3-3-3-1 subfields
              DSI 327      100 8 fields, 5-5 subfields
              IBM 733727   101 20 fields, 4 chars each
              IBM 888157   110 FORTRAN column layout

      Logo:   none                                  0000000 \ default may
              (your institution's logo here)        0000001 / vary!
              IBM 821924 (701 binary)
              IBM 821162 (701 assembly)
              IBM 874266 (7090 assembly)
              Rechenzentrum RWTH Aachen 
              University of Alaska
              University of Arizona Computer Center
              Battelle Laboratories
              Bell Labs (old style)
              Bell Labs (GE 600, new style)
A matter of philosophy: The forms listed in the forms category above are those which served as the basis for large numbers of institutional overprints! There were huge numbers of other standard forms, some of which should be probably be assigned as logos and overprinted on the blank form. As a result, these forms cannot have custom logos, but this should not cause great problems with users of the full-blown emulator package envisioned. Please, if you ever come up with keypunch emulators that support custom logos, inform me of the logos you use and reserve their numbers!