DICOM PS3.12 2024c - Media Formats and Physical Media for Media Interchange

A PC File System (Normative)

A.1 PC File System Mapping to Media Formats

Several of the removable media utilize the PC file system. For any media that use the PC file system, the following rules apply, except as overridden in the applicable annex.

A.1.1 File-set ID Mapping

The PC File System mapping does not provide a File-set ID.


On systems that permit user access to the media volume label, the volume label can be used to provide a File-set ID. Not all operating systems permit routine user access to this information.

A.1.2 File ID Mapping

The PC File System provides a hierarchical structure for directories and files within directories. Each structure has a root directory that may contain references to both files and sub-directories. Sub-directories may contain references to both files and other sub-directories. The nomenclature for referring to files and directories in the PC File System is:

  1. \ - For the root directory

  2. \filename - For a file in the root directory

  3. \subdir\filename - For a file in the sub-directory subdir

The PC File System name corresponding to a File ID shall be the DICOM File ID prefixed with the character "\", with the "\" character separating File ID components.


Example File ID mappings:

File ID

PC File system name







The DICOMDIR file shall be in the root directory for media that do not support multiple file-sets on a single medium. DICOMDIR location is described for the multiple file-set situation in the annex for such media.


It is recommended but not required that the File-set Descriptor File ID (0004,1141) be "README" (see PS3.10).

A.1.3 File Management Information

The PC File System provides the following information for each file:

Table A.1-1. PC File System File Information


1 to 8 characters


0 to 3 characters


Time of last modification (or creation)


Date of last modification (or creation)


Size of file (in bytes)

The PC File System Filename shall correspond to a DICOM File ID Component. The PC File System Extension for a DICOM file shall not contain any characters. The PC File System date and time shall be used to provide the DICOM facilities for examining the modification or creation date and time. Unused characters in Filename and Extension (see Table A.1-1) should be filled with null characters.


  1. The PC File System does not specify or control the time base used for date and time. Coordination of reference time zones is outside the scope of this Standard.

  2. The typical written form of a filename is filename.extension (e.g., "FILE.EXT"). The period between filename and extension is a convention used in most programs for entering and displaying the filename and extension. The period is not actually recorded on disk and is not permitted as part of a filename. A file with no extension is recorded as a file with zero extension characters (i.e., all null filled) although it is often written and displayed without the period.

The PC File system does not provide ownership or access control facilities. Write protection is addressed in the relevant physical media specific annex. Protection mechanisms are not available for the generic PC File System.

DICOM PS3.12 2024c - Media Formats and Physical Media for Media Interchange