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Elite on the BBC Micro

Save and load: DELT (Disc version)

Name: DELT [View in context] Type: Subroutine [Compare versions] Category: Save and load Summary: Catalogue a disc, ask for a filename to delete, and delete the file
This routine asks for a disc drive number, and if it is a valid number (0-3) it displays a catalogue of the disc in that drive. It then asks for a filename to delete, updates the OS command at DELI so that when that command is run, it it deletes the correct file, and then it does the deletion. Other entry points: DELT-1 \ Contains an RTS
.DELT JSR CATS \ Call CATS to ask for a drive number, catalogue that \ disc and update the catalogue command at CTLI BCS SVE \ If the C flag is set then an invalid drive number was \ entered as part of the catalogue process, so jump to \ SVE to display the disc access menu LDA CTLI+1 \ The call to CATS above put the drive number into STA DELI+4 \ CTLI+1, so copy the drive number into DELI+4 so that \ the drive number in the "DE.:0.E.1234567" string \ gets updated (i.e. the number after the colon) LDA #9 \ Print extended token 9 ("{clear bottom of screen}FILE JSR DETOK \ TO DELETE?") JSR MT26 \ Call MT26 to fetch a line of text from the keyboard \ to INWK+5, with the text length in Y TYA \ If no text was entered (Y = 0) then jump to SVE to BEQ SVE \ display the disc access menu \ We now copy the entered filename from INWK to DELI, so \ that it overwrites the filename part of the string, \ i.e. the "E.1234567" part of "DELETE:0.E.1234567" LDX #9 \ Set up a counter in X to count from 9 to 1, so that we \ copy the string starting at INWK+4+1 (i.e. INWK+5) to \ DELI+5+1 (i.e. DELI+6 onwards, or "E.1234567") .DELL1 LDA INWK+4,X \ Copy the X-th byte of INWK+4 to the X-th byte of STA DELI+5,X \ DELI+5 DEX \ Decrement the loop counter BNE DELL1 \ Loop back to DELL1 to copy the next character until we \ have copied the whole filename LDX #LO(DELI) \ Set (Y X) to point to the OS command at DELI, which LDY #HI(DELI) \ contains the DFS command for deleting this file JSR OSCLI \ Call OSCLI to execute the OS command at (Y X), which \ catalogues the disc JMP SVE \ Jump to SVE to display the disc access menu and return \ from the subroutine using a tail call