ico The .ICO filename extension refers to the ICON image file format originally developed by Microsoft. The extension is used to represent computer icon images of varying sizes designed for the operating system Microsoft Windows. Its use today has extended to developing icons for programs designed using the Microsoft developer's suite Visual Studio and other applications. Similar to other device independent bitmap file formats, the ICON file format is also in the raster graphics class of image formats where each individual pixel is part of an orthogonal dot matrix data structure with support for a limited palette of color information. As a resource file, the .ico file format has its strength in contextual use. This allows for multiple icon images of different color depth or size to be stored within the resource file and used when appropriate.
pcx The Picture Exchange file format, shortened PCX, with the .pcx filename extension is an image file format developed by ZSoft Corporation. It was initially released in 1985 as a lossless bitmap image format and for a time was the default file format for PC paintbrush. The format is now largely superseded by other formats given the target platforms for the software associated with the format are no longer in production, i.e. MS DOS and Windows 1.0.