File infector viruses: these infect program files, such as applications, games or utilities. They are often memory-resident, meaning that once they have been executed they remain active in the computer's memory and can infect more programs.
An executable file, like an .exe, can contain the virus and automatically launch whatever subroutine it uses to infect the system when you launch the application. A non-executable can in theory contain a virus that is passively inserted into the system when the file is utilized. At that stage, it’s hard to call it a virus as much as a potential virus that simply needs a host.
