Disk – Holding the Option Key at boot time activates a boot manager built into the firmware, where the user may choose from which drive/partition to boot the computer from, including Mac OS and Mac OS X partitions or drives on PowerPC-based Macs, and Mac OS X and Microsoft Windows partitions or drives on Intel-based Macs (running Mac OS X 10.4.6 and later with Boot Camp from Apple Inc. installed). This has been replaced by a general boot menu, activated by holding the power button on Apple Silicon-based Macs. The built-in bootloader can also boot other operating systems such as Linux; however, these are labeled as "Windows" in the bootloader. References Computer keys Macintosh platform