A floppy disk that is free of data. It can be placed in a Disk Drive to save either a computer's current RAM state or arbitrary data, or shapelessly crafted with redstone dust to make a FORTH Boot Disk.
To save a computer's current RAM state to disk using the FORTH command line, place a Blank Floppy in the active Disk Drive, then use the command
SAVE" DISK NAME". The Blank Floppy in the Disk Drive will be converted into a saved floppy with the item name "DISK NAME", or whatever string you choose. Note that if invalid characters are used in the disk name, it will be instead named "Unnamed". This saved state can be used as a new boot disk—but one containing all one's programs. It's advisable to save one's programs to a floppy once they're complete, as otherwise they will be lost if the computer is rebooted.