Save and load: LOD, Removed

       Name: LOD, Removed                                            [Show more]
       Type: Subroutine
   Category: Save and load
    Summary: Load a commander file
    Context: See this subroutine in context in the source code
 References: No direct references to this subroutine in this source file


 The filename should be stored at INWK, terminated with a carriage return (13).


                        \ --- Mod: Code removed for Demonstration Disc: ------->

\.LOD
\
\LDX #2                 \ Enable the ESCAPE key and clear memory if the BREAK
\JSR FX200              \ key is pressed (*FX 200,2)
\
\JSR ZERO               \ Zero-fill pages &9, &A, &B, &C and &D, which clears
\                       \ the ship data blocks, the ship line heap, the ship
\                       \ slots for the local bubble of universe, and various
\                       \ flight and ship status variables
\
\LDY #&B                \ Set up an OSFILE block at &0C00, containing:
\STY &0C03              \
\INC &0C0B              \ Load address = &00000B00 in &0C02 to &0C05
\                       \
\                       \ Length of file = &00000100 in &0C0A to &0C0D
\
\INY                    \ Increment Y to &C, which we use next
\
\LDA #&FF               \ Call QUS1 with A = &FF, Y = &C to load the commander
\JSR QUS1               \ file to address &0B00
\
\LDA &0B00              \ If the first byte of the loaded file has bit 7 set,
\BMI SPS1+1             \ jump to SPS+1, which is the second byte of an LDA #0
\                       \ instruction, i.e. a BRK instruction, which will force
\                       \ an interrupt to call the address in BRKV, which is set
\                       \ to BR1... so this instruction restarts the game from
\                       \ the title screen. Valid commander files for the
\                       \ cassette version of Elite only have 0 for the first
\                       \ byte, as there are no missions in this version, so
\                       \ having bit 7 set is invalid anyway
\
\LDX #NT%               \ We have successfully loaded the commander file at
\                       \ &0B00, so now we want to copy it to the last saved
\                       \ commander data block at NA%+8, so we set up a counter
\                       \ in X to copy NT% bytes
\
\.LOL1
\
\LDA &0B00,X            \ Copy the X-th byte of &0B00 to the X-th byte of NA%+8
\STA NA%+8,X
\
\DEX                    \ Decrement the loop counter
\
\BPL LOL1               \ Loop back until we have copied all NT% bytes
\
\LDX #3                 \ Fall through into FX200 to disable the ESCAPE key and
\                       \ clear memory if the BREAK key is pressed (*FX 200,3)
\                       \ and return from the subroutine there

                        \ --- End of removed code ----------------------------->