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HyperCard file format

Caveat Emptor!

Although originally intended by Bill Atkinson, the HyperCard file format has never been officially published. The instructions in this file are simply what was deduced by looking at various existing stacks and their differences.

Warning: The information in this document is not complete enough to allow the creation of new HyperCard stacks, but maybe it can be helpful in reading existing stacks and extracting precious data to keep it from being lost.

Prerequisites

Being a file format from Classic MacOS (shipped 1987 through 2004), many of the data types are from that era. All text is encoded in the MacRoman text encoding, and many flags and data types are from the Quickdraw headers, or based on them. All data is stored in Big-Endian format (like the Motorola 68000 used to do).

The block file layout

A HyperCard stack is a stream of blocks, with a four-character type code and a 4-byte signed ID number, terminated by a 'TAIL' block. Each block has the following basic layout:

4 byteBlock size
including size, type and ID.
4 bytesBlock type
4 bytesBlock ID number
n bytesBlock data

The Stack Block

There is one block in the file representing the stack object:

4 byteBlock size
including size, type and ID.
4 bytesBlock type 'STAK'
4 bytesBlock ID number -1
32 bytesThere be Tygers
4 bytesNumber of cards in this stack.
4 bytesThe ID of one card in the stack (why?).
4 bytesThe ID of the 'LIST' block in the stack.
16 bytesThere be Tygers
2 bytesThe User Level setting (1 ... 5) to run this stack under.
2 bytesThere be Tygers
2 bytesFlags: Bit 10 is cantPeek, 11 is cantAbort, 13 is privateAccess, 14 is cantDelete, 15 is cantModify.
18 bytesThere be Tygers
16 bytesThree 4-byte NumVersion entries containing the HyperCard version numbers that created, last edited or compacted this stack.
328 bytesThere be Tygers
2 bytesThe height in pixels of cards in this stack.
2 bytesThe width in pixels of cards in this stack.
262 bytesThere be Tygers

For each Pattern: (40 patterns, 320 bytes)

8 bytesRaw data for an 8x8 bitmap, with one byte representing one row.

512 bytesThere be Tygers
n bytesStack script as a C string, terminated by a NULL byte.

The Style Table

Styles for multi-styled text fields are stored as style formats in the style table block of the stack, and only referenced throughout the stack. Here's how the style table looks:

4 byteBlock size
including size, type and ID.
4 bytesBlock type 'STBL'
4 bytesBlock ID number
4 bytesThere be Tygers
4 bytesNumber of styles

For each style:

16 bytesThere be Tygers
2 bytesFont ID
-1 to indicate the font should be inherited from the containing field's styles.
2 bytesStyle flags
The high byte contains the standard Quickdraw font bits: bold, italic, underline, outline, shadow, condense, extend, group. If both bytes are 0xFF, the style is unset and should be inherited from the field's styles.
2 bytesFont Size
-1 to indicate the size should be inherited from the containing field's styles.
2 bytesThere be Tygers

The Font Table

Since font IDs are not persistent across systems, HyperCard contains a table mapping font names to IDs, so it can get away with storing font IDs in the stack file, but still map the ID to the new one when it changes. The table looks like this

4 byteBlock size
including size, type and ID.
4 bytesBlock type 'FTBL'
4 bytesBlock ID number
6 bytesThere be Tygers
2 bytesNumber of fonts
4 bytesThere be Tygers

For each font:

2 bytesFont ID
1 byteLength of name
n bytesName of the font
0...1 bytesAlignment byte

The Page Table List

Cards may be stored in an arbitrary order in a stack, so there is list of pages that, among other things, contains an ordered list of the card IDs in this stack. To speed up insertions/deletions of cards in large stacks, this list has been segmented. There is one 'LIST' block listing all page tables, and then a bunch of page table blocks listing the cards in order. Here's the list block's format:

4 byteBlock size
including size, type and ID.
4 bytesBlock type 'LIST'
4 bytesBlock ID number
4 bytesNumber of page tables
8 bytesThere be Tygers
2 bytesSize of card blocks
16 bytesThere be Tygers

For each page table:

2 bytesThere be Tygers
4 bytesID of 'PAGE' block


 

The Page Table

The page table stores the order of the cards in the stack (because the actual card data is kept in an arbitrary order in the file) and is segmented into several blocks. Each block looks like the following:

4 bytesBlock size
including size, type and ID.
4 bytesBlock type 'PAGE'
4 bytesBlock ID number
12 bytesThere be Tygers

For each card (get the count from the STAK block):

4 bytesCard ID
1 byteCard flags, where bit 5 contains the marked of the card.
n bytesThere be Tygers
(where n is the "Size of card blocks" from the 'PAGE' block, minus the 5 bytes for card ID and flags)


 

Cards and Backgrounds

Both cards and backgrounds are stored in the following kind of block:

4 bytesBlock size
including size, type and ID.
4 bytesBlock type 'CARD' or 'BKGD'
4 bytesBlock ID number
4 bytesThere be Tygers
4 bytesID of BMAP block for card picture (0 means all transparent)
2 bytesFlags. Bit 14 is cantDelete, 13 is hide card picture, 11 is dontSearch,
14 bytesThere be Tygers
4 bytesID of background for this card
2 bytesNumber of parts on this card
6 bytesThere be Tygers
2 bytesNumber of part contents on this card
4 bytesScript Type: If 0 HyperTalk, if 'WOSA' the card has a compiled OSA language script (e.g. AppleScript).

For each part:

2 bytesLength in bytes of this part entry
1 byteType: 1: button 2: field
1 byteFlags: Bit 7 is hidden, bit 5 is dontWrap, 4 is dontSearch, 3 is sharedText, 2 is fixedLineHeight, 1 is autoTab, 0 is disabled/lockText
2 bytesTop coordinate of part rectangle.
2 bytesLeft coordinate of part rectangle.
2 bytesBottom coordinate of part rectangle.
2 bytesRight coordinate of part rectangle.
2 bytesMore flags: bit 15 is showName/autoSelect, bit 14 is highlight/showLines, bit 13 is wideMargins/autoHighlight, bit 12 is sharedHighlight/multipleLines, bits 11 through 8 is the button family number
Low 4 bits = style:
Buttons: 0 is transparent, 1 is opaque, 2 is rectangle, 3 is roundrect, 4 is shadow, 5 is checkbox, 6 is radiobutton, 8 is standard, 9 is default, 10 is oval, 11 is popup.
Fields: 0 is transparent, 1 is opaque, 2 is rectangle, 4 is shadow, 7 is scrolling.
2 bytestitleWidth/lastSelectedLine
2 bytesicon ID/(first)SelectedLine
2 bytestextAlignment: 0 left (or default?), 1 center, -1 right, (-2 force left align?)
2 bytestextFont ID
2 bytestext font size
2 bytesline height
2 bytestext style flags: bit 15 is group, 14 is extend, 13 is condense, 12 is shadow, 11 is outline, 10 is underline, 9 is italic, 8 is bold
2 bytesline height
n bytesName of the part as a zero-terminated C string.
n bytesScript of the part as a zero-terminated C string.
0 ... 1 bytesAignment byte, if needed.

For each part content entry:

2 bytesPart ID (of part these contents belong to)
If this is < 0, this is an entry for a card part (take partID * -1), otherwise for a background part.
2 bytesLength of this contents entry.
2 bytesLength of styles
If this is > 32767, there is stylesLength -32770 bytes of style data prepended to the text, otherwise the text is mono-styled.

Style data is stylesLength / 4 entries like:

2 bytesstart offset
2 bytesindex into 'STBL' block

n bytesText data

n bytesName of the card as a zero-terminated C string.
n bytesScript of the card as a zero-terminated C string.

Optional OSA script data:

2 bytesOffset from end of this field to OSA script (jump across header)
2 bytesLength of OSA script
n bytesRemainder of header
n bytesOSA Script


 

If you have found out more about this file format, feel free to amend this document and let us know.
 


Written up by Mister Z.
 
A day of acquaintance, And then the longer span of custom. But first -- The hour of astonishment.