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Elite on the BBC Micro

Save and load: QUS1 [Cassette version]

Name: QUS1 [Show more] Type: Subroutine Category: Save and load Summary: Save or load the commander file Deep dive: Commander save files
Context: See this subroutine in context in the source code Variations: See code variations for this subroutine in the different versions References: This subroutine is called as follows: * LOD calls QUS1 * SVE calls QUS1

The filename should be stored at INWK, terminated with a carriage return (13). The routine should be called with Y set to &C. Arguments: A File operation to be performed. Can be one of the following: * 0 (save file) * &FF (load file) Y Points to the page number containing the OSFILE block, which must be &C because that's where the pointer to the filename in INWK is stored below (by the STX &0C00 instruction)
.QUS1 LDX #INWK \ Store a pointer to INWK at the start of the block at STX &0C00 \ &0C00, storing #INWK in the low byte because INWK is \ in zero page LDX #0 \ Set X to 0 so (Y X) = &0C00 JMP OSFILE \ Jump to OSFILE to do the file operation specified in \ &0C00 (i.e. save or load a file depending on the value \ of A), returning from the subroutine using a tail call