A computer virus does not need another program to survive; it hides within programs only to avoid detection. Comparing computer virus with a biologic life form the computer virus is far more sophisticated; it’s more like an insect. Neither of them can learn, but both a computer virus and insects has basic status memories and can act on input. A biologic virus cannot act on input. A computer virus can attach to the keyboard driver and do an action like ctrl-alt-del -> format c: and a ant can trigger on the smell that leads back to a its hill. But the ant can never learn another way to find its hill without that specific smell, and a virus will not run format c: without the predefined trigger.