# DDI

> sector-based disk image format

**Wikidata**: [Q28600458](https://www.wikidata.org/wiki/Q28600458)  
**Source**: https://4ort.xyz/entity/ddi

## Summary
DDI (DiskDupe Image) is a sector-based disk image format used to create exact copies of disk volumes, preserving their structure and content. It is identified by the `.ddi` file extension and stores data in a raw, unprocessed form. DDI ensures precise replication of disks, including boot sectors and file systems.

## Key Facts
- DDI is a sector-based disk image format designed for exact disk replication.
- Also known as **DiskDupe Image**.
- Uses the `.ddi` file extension.
- Media type: `application/octet-stream`.
- Identified by the hexadecimal signature `4D534420496D6167652056657273696F6E2031` at the start of the file.
- Recognized by tools like TrID scan (reference: https://mark0.net/soft-tridscan-e.html).
- Instance of **disk image**, a file type that mirrors a physical disk's structure and data.

## FAQs
### Q: What is DDI used for?
A: DDI is used to create sector-level copies of disks, ensuring all data—including boot records and file systems—is preserved. This makes it useful for backups, cloning, and software distribution.

### Q: How do I identify a DDI file?
A: DDI files use the `.ddi` extension and start with the hexadecimal signature `4D534420496D6167652056657273696F6E2031`.

### Q: Is DDI still widely used?
A: While newer formats like ISO or DMG are more common today, DDI remains relevant for legacy systems, emulation, and specific disk-cloning tasks.

## Why It Matters
DDI plays a critical role in scenarios requiring precise disk replication, such as software preservation, system recovery, and forensic analysis. By capturing disk data at the sector level, DDI ensures that even hidden or non-file system data (e.g., bootloaders) is retained. This reliability made it valuable for distributing software on physical media and for restoring systems to a known state. While modern formats have surpassed it in popularity, DDI’s simplicity and accuracy keep it relevant in niche applications.

## Notable For
- **Sector-based imaging**: Captures raw disk data, including gaps between files and system-specific sectors.
- **Legacy association**: Linked to DiskDupe, a tool historically used for duplicating floppy disks.
- **Unique file signature**: Its identifying hex pattern distinguishes it from other disk image formats.
- **Specialized use cases**: Valued in emulation, retrocomputing, and archival of obsolete media.

## Body
### Technical Specifications
- **Format Type**: Sector-based disk image.
- **File Extension**: `.ddi`.
- **Media Type**: `application/octet-stream`.
- **Data Structure**: Stores raw byte-by-byte copies of disk sectors.

### File Identification
- **Hex Signature**: Begins with `4D534420496D6167652056657273696F6E2031` (ASCII: "MSD Image Version 1").
- **Detection Tools**: Identifiable via utilities like TrID, which analyze file headers.

### Usage Context
- **Backup and Cloning**: Preserves entire disk states for recovery or deployment.
- **Legacy Systems**: Used for duplicating floppy disks or bootable media.
- **Emulation**: Enables running legacy software by replicating original disk structures.

## References

1. [TrID](https://mark0.net/soft-tridscan-e.html)