.ICL

Introduction

An ICL file is a collection of Windows icons in one file. Icon editors of the 1990s used it to share icon sets, and it is still met in icon packs. Windows can pick an icon out of an ICL file in the Change Icon dialog, the same way it picks one out of a program or a DLL.

The file is not a new format at all: it is a 16-bit Windows library with no code, only icon resources, given a different extension.

Structure

An ICL file is a New Executable (NE) file. It starts with an MS-DOS MZ header whose pointer at offset 0x3C leads to the NE header. The NE resource table lists the icons. Each icon is stored the way it is in a program: a group icon resource that lists the sizes, and one icon resource per size holding the bitmap, much like an entry in an ICO file.

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