Decompiling is rarely perfect. The resulting code is often "equivalent" rather than "exact," meaning it functions the same way but may look different from the original source code.
The Nintendo DS (often abbreviated as or simply DS) boasts one of the most beloved libraries in gaming history. For developers, hackers, and enthusiasts, accessing the core code of these games is a crucial part of creating mods, translating titles, or understanding how complex logic was packed into a handheld device.
arm7.bin : Code for the secondary processor (handles audio and Wi-Fi).
: For the actual decompilation, Ghidra is the community favorite. By using specialized plugins like NTRGhidra , you can load DS-specific memory maps and have Ghidra automatically translate ARM assembly into readable C code.
Extracting text and inserting translated dialogue. nds decompiler
undefined * FUN_02001234(void) // What is 0x04000000? It's the display controller. *(undefined2 *)0x4000000 = 0; return &DAT_02001240;
Retail NDS games do not include function names or variable titles. You will see names like FUN_020004a2 instead of Player_CalculateDamage . You must manually deduce what functions do based on their behavior and rename them.
have a decompilation project that builds the complete US ROMs from reconstructed source code. The repository shows the significant effort involved—78.8% assembly, 13.9% C, 5.9% C++, reflecting the painstaking process of converting machine code back to readable C.
Decompilation exists in a complex legal space. Game code is copyrighted intellectual property, and the process of reverse engineering can potentially infringe on those rights. However, several factors may provide legal cover for responsible decompilation efforts. Decompiling is rarely perfect
: Clocked at 67 MHz, this chip handles the majority of the game logic, 3D graphics rendering, and major calculation engines.
ROM files directly into Ghidra, handling the complex memory mapping for you.
: A free, open-source tool developed by the NSA that includes a powerful decompiler for ARM architectures.
Usually runs a smaller, more standardized subsystem or BIOS-level code. For developers, hackers, and enthusiasts, accessing the core
Let us walk through a real example. Assume you extracted arm9.bin from a commercial ROM using ndstool .
NDS decompilation is not a trivial task. Several key challenges persist, explaining why there is no perfect, automated decompiler:
For many veteran ROM hackers, (often stylized as NO$GBA) is the gold standard. Originally developed by Martin Korth as a Game Boy Advance emulator, its debugging capabilities for the Nintendo DS are unparalleled. It was historically a commercial product, but recent releases have become freeware, opening its powerful feature set to a wider audience.
This practice exists in a legal gray area that requires careful consideration. While creating personal backups is often permitted, distributing ROMs is illegal. Decompiled code is considered a derivative work, making public distribution potentially infringing on copyright. This is why many decompilation projects, like pret for Pokémon, use a clean-room approach: one person documents the game's behavior, and a second writes new, original code based only on that documentation. For ethical learning, you should always: