Windows DDB

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File Format
Name Windows DDB
Extension(s) .ddb, .bmp
PRONOM fmt/114
Released 1985

Windows DDB (Device-Dependent Bitmap), or Windows BMP v1, is a graphics format associated with Microsoft Windows 1.0. It has only a little in common with the BMP formats that succeeded it.

This article covers both a particular file format, and the BITMAP structure on which it is based (which may be embedded in other formats).


BITMAP structure

Originally named BITMAP, the structure is often called BITMAP16, to distinguish it from the versions of BITMAP associated with later operating systems.

The structure is 14 bytes in size, with the last 4 bytes ("bmBits") being a memory pointer to the bitmap pixels.

In a file on disk, the bmBits field is usually not used (it's not clear whether some formats omit it entirely). The pixel data usually immediately follows.


Offset Type Meaning
0x0000 WORD bmType
0x0002 WORD bmWidth: Width in pixels
0x0004 WORD bmHeight: Height in pixels
0x0006 WORD bmWidthBytes: Width of a line in bytes
0x0008 BYTE bmPlanes: Number of planes in bitmap
0x0009 BYTE bmBitsPixel: Number of bits per pixel
0x00A0 DWORD bmBits: Pointer to pixels

Other formats that can contain this structure include HLP (via SHG), WRI, WMF, and resources in EXE/NE files of that era.

DDB file format

Bitmap files in this format can be found in the Windows 2 DDK.

This format is not the format saved by Windows 1.0 Paint. It is generated by ICONEDIT, the Windows 1.x icon / cursor / bitmap editor.

Files begin with a 16-byte header, the last 14 bytes of which correspond to the BITMAP structure:

Offset Type Meaning
0x0000 WORD File type: 0x0002, RT_BITMAP. Top bit set if discardable.
0x0002 BITMAP16 Refer to BITMAP16, above.
bmType: Always 0x0000 for main memory bitmap
bmBits: Always zero in disk file

This is followed by the bitmap, in top-to-bottom order, with bmWidthBytes bytes per line.



  • The MSWrite decoder from libwps appears to have source code for reading embedded DDB objects.


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