The hole in a floppy disk is called the 'index hole.' It is a small, circular hole located near the center of the floppy disk that is used to detect the beginning of each track on the disk. A sensor inside the floppy drive detects the index hole as the disk spins and uses it to determine the start of each track.
The envelope or case that protects the floppy disk is called a 'sleeve.' The sleeve is usually made of paper or plastic and is used to protect the disk from dust, dirt, and scratches. The sleeve also has a small window that allows the user to see the label on the disk and identify its contents. Some sleeves may also have additional features such as a flap to seal the sleeve or a pocket to hold additional documentation.
