.DEEOR LDA #LO(DOENTRY-1) \ Set FRIN(1 0) = DEEORS-1 as the low address of the STA FRIN \ decryption block, so we decrypt from just after the LDA #HI(DOENTRY-1) \ DEEORS routine STA FRIN+1 LDA #HI(F%-1) \ Set (A Y) to F% as the high address of the decryption LDY #LO(F%-1) \ block, so we decrypt to the end of the main game code \ at F% LDX #&19 \ Set X = &19 as the decryption seed (the value used to \ encrypt the code, which is done in elite-checksum.py) JSR DEEORS \ Call DEEORS to decrypt between DOENTRY and F% LDA #LO(XX21-1) \ Set FRIN(1 0) = XX21-1 as the low address of the STA FRIN \ decryption block LDA #HI(XX21-1) STA FRIN+1 LDA #&B1 \ Set (A Y) = &B1FF as the high address of the LDY #&FF \ decryption block LDX #&62 \ Set X = &62 as the decryption seed (the value used to \ encrypt the code, which is done in elite-checksum.py) \ Fall through into DEEORS to decrypt between XX21 and \ &B1FFName: DEEOR [Show more] Type: Subroutine Category: Utility routines Summary: Unscramble the main codeContext: See this subroutine in context in the source code References: This subroutine is called as follows: * S% calls DEEOR
The main game code and data are encrypted. This routine decrypts the game code in two parts: the main game code between DOENTRY and F%, and the game data between XX21 and the end of the game data at &BFFF. In the BeebAsm version, the encryption is done by elite-checksum.py, but in the original this would have been done by the BBC BASIC build scripts.
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Subroutine DEEORS (category: Utility routines)
Decrypt a multi-page block of memory
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Subroutine DOENTRY (category: Flight)
Dock at the space station, show the ship hangar and work out any mission progression
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Variable F% (category: Utility routines)
Denotes the end of the main game code, from Elite A to Elite H
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Configuration variable XX21 = &8000
The address of the ship blueprints lookup table, as set in elite-data.asm