In most cases, the PowerPC code will be located in the data fork of the executable, and 680 x 0 code will be located in the resource fork. There are currently three basic types of MacOS executables. They are 680 x 0 native, PowerPC native, and Fat. 680 x 0 native applications do not contain native PowerPC code, but can be emulated on the PowerMacintosh. PowerPC native applications do not contain any 680 x 0 code, and are incompatible with earlier Macintoshes.
Fat applications contain native code for both platforms.
Some older MacOS viruses are unsuccessful on PowerPC-based Macintoshes. While they are written in 680 x 0 code capable of executing inside the PowerMac emulator, the viruses fail to update the code fragment resource in newer executables to make their code active. On 680 x 0 machines, an error dialog will appear and the virus will fail to execute. However, future variants could easily be designed to operate on all Macintoshes. Developing a Conscience The four known AutoStart 9805 variants share a common replication mechanism, but the behaviour of each is unique.