Save and load: DELT

       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
 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