1DD File

What are 1DD files and how to open them

Are you having problems opening a 1DD file or are you simply curious about its contents? We're here to explain the properties of these files and provide you with software that can open or handle your 1DD files.

What is a 1DD file?

A .1DD file is a SMC-777 Disk Image file.

SMC-777 Disk Image files with extension .1DD store the full contents of a single-sided, single-density floppy disk used by the SONY SMC-777 home computer. These images replicate every byte from the disk's sectors so emulators or disk utilities can read the disk data exactly as the original hardware would.

Files are created by dumping or converting actual SMC-777 floppies, or produced in compatible disk image tools. Common usage is in emulation (for example, with the WinSMC emulator) or when using disk-image utilities to write or manipulate virtual copies of SMC-777 disks. They may be converted from the .1DD form into raw binary or other image types when needed.

The disk geometry for a standard .1DD image is 70 tracks, single-sided (1 head), 16 sectors per track, with 256-byte sectors. The total data payload is thus 70 × 16 × 256 bytes. Internal identifiers in these images include distinctive byte signatures at specific offsets: one starting around offset 7 showing repeating track/sector headers, and another at offset 688 marking the disk-type or density byte.

How to open 1DD files

Important: Different programs may use files with the 1DD file extension for different purposes, so unless you are sure which format your 1DD file is, you may need to try a few different programs.

We have not yet verified any programs for Windows that work with this specific file format. If you know one, please use the 'Suggest a program' link below. Thanks!

Last updated: August 14, 2026

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