I am reading a book, learning about how booting in computer works. One of the snippets in book mentions about how firmware proceeds with boot process while booting a computer.
Some context on what i am reading :
BIOS The BIOS boot process begins with the computer reading a boot sector (typically the first sector) from a disk and then executing that code. Thus, boot options for BIOS-based computers are limited; you can only select the order in which various boot devices (hard disks, optical disks, USB devices, network boot, and so on) are examined to find a boot sector.
It later mentions about various issues associated with removable disks used for boot sequences (check below)
Although boot sequences involving removable disks are common, they have their problems. For instance, if somebody accidentally leaves a CD or DVD in the drive, this can prevent the system from booting.
The book does not elaborate on why keeping CD/DVD in the drive cause the system from booting. Can someone throw some light on this topic ?