[notacoward]

The extreme case is programs for which the entire platform has been abandoned - e.g. DOS (including TSRs), old Windows, old MacOS (including desk accessories). There's a whole "abandonware" community devoted to preserving games that have rotted this way, usually relying on emulation to keep them from being forgotten entirely. There are various file compression/encryption/annotation utilities that have become unusable because they relied on deprecated Windows APIs. Various sound/video hacks on Linux have died as those subsystems remain in constant flux. In my own work as a Gluster maintainer, several pieces such as Java/Python or monitoring APIs have rotted away as those APIs changed. It usually takes a long time for a large program to rot away completely, but individual pieces can become non-functional long before then.