FDF Image

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==Specifications==
 
==Specifications==
−
The FDF file format is reverse engineered in 86Box, the source code can be found at  
+
The FDF file format is reverse engineered in 86Box, the source code can be found at:
 
  86Box-master\src\floppy\fdd_img.c
 
  86Box-master\src\floppy\fdd_img.c
 +
 +
Basically FDF used RLE compression.
 +
 +
Integers are stored as little-endian.
 +
 +
EZ-DisKlone truncates the image, the unused sectors filled with 0xF6 at end of the disk are not stored.
 +
 +
* Each track/head is stored as a block.
 +
* So number of bytes per block is equal to number of bytes per track.
 +
* If two heads then the number of blocks is even.
 +
* The number of stored blocks is equal/less then the number of track/heads.
 +
* The number of stored tracks is in the file header.
 +
* The CHS geometry is derived from the DiskType field.
 +
 +
 +
//------------------------------------------------------------------------------
 +
// Limits
 +
//------------------------------------------------------------------------------
 +
 +
// string lengths
 +
#define FDFFILE_LEN_DESCR    64
 +
 +
// sector size
 +
#define FDFFILE_SECTOR_SIZE  512
 +
 +
 +
//------------------------------------------------------------------------------
 +
// File header
 +
//------------------------------------------------------------------------------
 +
 +
// file signature
 +
#define FDFFILE_SIGNATURE  MAKE_FOURCC(0x1A, 'F', 'D', 'F')
 +
 +
// disk (geometry) types
 +
#define FDFFILE_DT_360K    0x03  /* 40/2/9  = 4608 bytes/track */
 +
#define FDFFILE_DT_720K    0x04  /* 80/2/9  = 4608 bytes/track */
 +
#define FDFFILE_DT_120M    0x05  /* 80/2/15 = 7680 bytes/track */
 +
#define FDFFILE_DT_144M    0x06  /* 80/2/18 = 9216 bytes/track */
 +
 +
 +
// file header
 +
// - 128 bytes
 +
typedef struct
 +
{
 +
  // equal to FDFFILE_SIGNATURE
 +
  UINT32 Signature;
 +
 +
  // always zero
 +
  UINT8  Reserved1;
 +
 +
  // one of FDFFILE_DT_xxx
 +
  UINT8  DiskType;
 +
 +
  // description
 +
  CHAR  Descr[FDFFILE_LEN_DESCR];
 +
 +
  // all zero
 +
  UINT8  Reserved2[8];
 +
 +
  // unknown (0x0100)
 +
  UINT16 Unknown1;
 +
 +
  // number of stored tracks
 +
  // - must be multiplied by number of heads to get number of blocks
 +
  UINT16 TrackCnt;
 +
 +
  // all zero
 +
  UINT8  Reserved3[46];
 +
 +
  //
 +
} TFdfFile_FileHdr;
 +
 +
 +
//------------------------------------------------------------------------------
 +
// Block header
 +
//------------------------------------------------------------------------------
 +
 +
// block compression method
 +
#define FDFFILE_METHOD_STORED  0x00
 +
#define FDFFILE_METHOD_RLE      0x01
 +
#define FDFFILE_METHOD_EOD      0xFF  /* end of data */
 +
 +
 +
// block header
 +
// - 5 bytes
 +
// - followed by RLE compressed data
 +
typedef struct
 +
{
 +
  // one of FDFFILE_METHOD_xxx
 +
  UINT8  Method;
 +
 +
  // CRC16L checksum (LHA)
 +
  UINT16 CRC;
 +
 +
  // number of compressed bytes
 +
  UINT16 Size;
 +
 +
  //
 +
} TFdfFile_BlkHdr;
 +
 +
 +
 +
//------------------------------------------------------------------------------
 +
// RLE compression
 +
//------------------------------------------------------------------------------
 +
// - if FDFFILE_METHOD_EOD    then end of file
 +
// - if FDFFILE_METHOD_STORED then block is stored uncompressed
 +
// - if FDFFILE_METHOD_RLE    then:
 +
//  * if b7 is set then the lower 7 bits are the repeat count and the next
 +
//    byte is the byte to repeat
 +
//  * If b7 is zero then its a store count, followed by the stored bytes
 +
//------------------------------------------------------------------------------
  
 
==Software==
 
==Software==
 
* [https://archive.org/details/EZDKP40_ZIP Software download and Emulation]
 
* [https://archive.org/details/EZDKP40_ZIP Software download and Emulation]
  
−
==Sample File==
+
==Sample Files==
 
* [https://archive.org/download/UtilitiesRom2/BB_94%20%28G%29.zip/BB_94%20%28G%29%2F1234%2F1234.FDF DOS Mouse Driver Image file]
 
* [https://archive.org/download/UtilitiesRom2/BB_94%20%28G%29.zip/BB_94%20%28G%29%2F1234%2F1234.FDF DOS Mouse Driver Image file]
 +
* {{DexvertSamples|archive/floppyDiskFile}}
  
 
==Links==
 
==Links==
 
* [http://www.ez-forms.com/ezdkp.htm EZX's EZ-DisKlone™ Plus for DOS]
 
* [http://www.ez-forms.com/ezdkp.htm EZX's EZ-DisKlone™ Plus for DOS]
 
* SSW/EZX's Super DiskCopy
 
* SSW/EZX's Super DiskCopy

Latest revision as of 17:31, 22 September 2026

File Format
Name FDF Image
Ontology
Extension(s) .fdf
Released 1991

Contents

[edit] Overview

Floppy Disk File (FDF) are disk images used by the DOS software EZ-DisKlone Plus. Introduced in 1991, the format is a compressed disk image validated by a 16bit CRC.

[edit] File Identification

FDF files have the header "1A 46 44 46".

[edit] Specifications

The FDF file format is reverse engineered in 86Box, the source code can be found at: 

86Box-master\src\floppy\fdd_img.c

Basically FDF used RLE compression.

Integers are stored as little-endian.

EZ-DisKlone truncates the image, the unused sectors filled with 0xF6 at end of the disk are not stored.

  • Each track/head is stored as a block.
  • So number of bytes per block is equal to number of bytes per track.
  • If two heads then the number of blocks is even.
  • The number of stored blocks is equal/less then the number of track/heads.
  • The number of stored tracks is in the file header.
  • The CHS geometry is derived from the DiskType field. 


//------------------------------------------------------------------------------
// Limits
//------------------------------------------------------------------------------

// string lengths
#define FDFFILE_LEN_DESCR     64

// sector size
#define FDFFILE_SECTOR_SIZE  512


//------------------------------------------------------------------------------
// File header
//------------------------------------------------------------------------------

// file signature
#define FDFFILE_SIGNATURE   MAKE_FOURCC(0x1A, 'F', 'D', 'F')

// disk (geometry) types
#define FDFFILE_DT_360K    0x03   /* 40/2/9  = 4608 bytes/track */
#define FDFFILE_DT_720K    0x04   /* 80/2/9  = 4608 bytes/track */
#define FDFFILE_DT_120M    0x05   /* 80/2/15 = 7680 bytes/track */
#define FDFFILE_DT_144M    0x06   /* 80/2/18 = 9216 bytes/track */


// file header
// - 128 bytes
typedef struct
{
  // equal to FDFFILE_SIGNATURE
  UINT32 Signature;

  // always zero
  UINT8  Reserved1;

  // one of FDFFILE_DT_xxx
  UINT8  DiskType;

  // description
  CHAR   Descr[FDFFILE_LEN_DESCR];

  // all zero
  UINT8  Reserved2[8];

  // unknown (0x0100)
  UINT16 Unknown1;

  // number of stored tracks
  // - must be multiplied by number of heads to get number of blocks
  UINT16 TrackCnt;

  // all zero
  UINT8  Reserved3[46];

  //
} TFdfFile_FileHdr;


//------------------------------------------------------------------------------
// Block header
//------------------------------------------------------------------------------

// block compression method
#define FDFFILE_METHOD_STORED   0x00
#define FDFFILE_METHOD_RLE      0x01
#define FDFFILE_METHOD_EOD      0xFF   /* end of data */


// block header
// - 5 bytes
// - followed by RLE compressed data
typedef struct
{
  // one of FDFFILE_METHOD_xxx
  UINT8  Method;

  // CRC16L checksum (LHA)
  UINT16 CRC;

  // number of compressed bytes
  UINT16 Size;

  //
} TFdfFile_BlkHdr;



//------------------------------------------------------------------------------
// RLE compression
//------------------------------------------------------------------------------
// - if FDFFILE_METHOD_EOD    then end of file
// - if FDFFILE_METHOD_STORED then block is stored uncompressed
// - if FDFFILE_METHOD_RLE    then:
//   * if b7 is set then the lower 7 bits are the repeat count and the next
//     byte is the byte to repeat
//   * If b7 is zero then its a store count, followed by the stored bytes
//------------------------------------------------------------------------------

[edit] Software

[edit] Sample Files

[edit] Links

Retrieved from "http://fileformats.archiveteam.org/index.php?title=FDF_Image&oldid=52090"
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