D64

D64 is a disk image format used to represent the contents and physical structure of a Commodore 64/128 5.25-inch floppy disk. It is widely used for emulation, software preservation, and archival distribution, and typically carries the file extension .d64. A D64 image captures the data stored on each disk sector and the track layout, enabling exact reproduction of the original disk’s contents when loaded into a compatible emulator.

Technically, a standard D64 image models a single-sided disk with 35 tracks and up to 21 256-byte sectors per track. The image includes the data in every sector and a map of which sectors are used, along with the disk’s directory information that describes files and their starting sectors. Emulators interpret this information to reconstruct the file system and allow access to individual files as they were on the physical disk. Because D64 represents raw sector data and layout, it can faithfully reproduce most software stored on CBM DOS-formatted disks.

Usage and scope: D64 images are commonly created by dumping a real disk or assembling data from multiple sources for archival purposes. They are supported by major Commodore 64 emulators such as VICE and CCS64, as well as by various image-management and conversion tools. While D64 provides a sector-level copy for accurate reproduction, some copy-protected or timing-sensitive disks may require alternative formats to preserve all hardware-specific behavior.

Variants and related formats: Other CBM DOS-based image formats include D71 for double-sided 5.25-inch disks (70 tracks) and D81 for certain 3.5-inch disk configurations. For sector-exact or timing-critical preservation, formats such as G64 are used. D64 remains the most common format for distributing single-sided Commodore disk images.