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⌂ ∞ Elite on the BBC Micro

Save and load: DELT [BBC Micro disc version, Docked]

       Name: DELT                                                    [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Catalogue a disc, ask for a filename to delete, and delete the
             file

    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:
             * SVE calls DELT
             * CATS calls entry point DELT-1




 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 (or a directory
                        \ name on the Master Compact) and catalogue that disc
                        \ or directory

 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 "DE.: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