Family Computer Disk System

iNES was an early NES emulator developed by Marat Fayzullin. Its most lasting contribution to the NES scene was its ROM file format and mapper numbering system.

.FDS format

The FDS format (file name suffix .fds) is a way to store Famicom Disk System disk data. It consists of the following sections, in order:

1. Header (16 bytes)
2. Disk data (65500 * x bytes)

The format of the header is as follows:

• 0-3: Constant $46 $44 $53 $1A ("FDS" followed by MS-DOS end-of-file)
• 4: Number of disk sides in 65500 byte units
• 5-15: Zero filled

References

• FDS Lister by ccovell
• iNES header/format by VmprHntrD