Which file type is commonly used as a virtual medium to install software without a physical disk?

• A. ISO file
• B. ZIP file
• C. EXE installer
• D. DMG file

Answer: (A)

Understanding how disk images work helps explain this. An ISO file is a complete copy of a CD or DVD’s contents and structure. When you mount an ISO, the operating system treats it as if a physical disc has been inserted, so you can run installers or access software files directly without touching a real disc. This makes ISO a universal and convenient virtual medium for software distribution, since it can be mounted on Windows, macOS, and Linux, or burned to a disc if needed. The other options don’t fit as well: ZIP is just a compressed package that needs extraction and doesn’t reproduce a disc’s filesystem; an EXE installer is an executable program, not a disc image; and DMG is a macOS-specific disk image. So the file type commonly used as the virtual medium is the ISO file.