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Author: Technical Research Division (Retro Gaming Preservation) Date: October 2023 Subject: Reverse Engineering & ROM Hacking Abstract The usrcheat.dat file is the proprietary database format used by the NDS emulator DeSmuME and various flashcart kernels (such as YSMenu and Wood R4) to store Action Replay (AR) cheat codes. Unlike raw XML or text files, this format requires specific hashing, compression, and structural alignment. This paper provides a rigorous methodology for extracting, editing, and injecting custom cheat codes into the usrcheat.dat file without corrupting the database integrity. 1. Introduction Cheat codes for the Nintendo DS operate via memory patches applied by the emulator or cartridge kernel. The usrcheat.dat file aggregates thousands of game entries, each containing a unique Game ID (a 4-byte CRC32 hash) and a series of Action Replay v3 codes. Directly editing the binary is impossible; thus, an intermediate toolchain is required. 2. Required Tools To modify usrcheat.dat , one must use software that understands the proprietary CCF (Cheat Code Format) or R4cce structures.