For OFS3 files, i found that in a website :
OFS3 header (16-bytes)
0x00: [4-bytes] OFS3 file signature (it's always 4F46 5333)
0x04: [4-bytes] OFS3 Header size (it's always 1000 0000)
0x08: [4-bytes] Unknown value
0x0c: [4-bytes] Nametable Start address (this points to the end of the file if...