Windows 1.0 Icon

The Windows 1.x variant of the ICO format is used in Microsoft Windows versions 1 and 2 to define monochrome icons. It has little in common with the ICO format used by Windows 3 and above.

Format
Files begin with a little-endian word, which is one of:

This is followed by a 12-byte header describing the icon bitmap: Two bitmaps come after the header, each  *   bytes long. The first bitmap is ANDed with the screen pattern; then the second is XORed on top of it.

A file in 'device independent' format is stored at double its eventual size (so a 32&times;32 icon would be saved as a 64&times;64 bitmap). A file in 'Both formats' format contains the header and bitmaps for the 'device-independent' version of the bitmap, followed by the header and bitmaps for the 'device-dependent' version.

Sample files

 * Samples can be found in the Windows 2.x DDK, or generated with the Windows 1.x / 2.x icon editor ICONEDIT.