The storage layout of a disk as determined by its physical medium and as initialized by a format program. Disk formats can be obviously different; for example, a 3.5" floppy compared to the earlier 5.25" floppy. However, a 3.5" floppy could be a Windows disk or a Mac disk depending on which system initialized it. See low-level format, high-level format, DOS/Windows format, DOS Format and file format.