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⌂ ∞ Elite on the BBC Micro and NES

Version analysis of prx

This code appears in the following versions (click to see it in the source code):

Code variations between these versions are shown below.

       Name: prx
       Type: Subroutine
   Category: Equipment
    Summary: Return the price of a piece of equipment



 This routine returns the price of equipment as listed in the table at PRXS.



 Arguments:

Code variation 1 of 1A variation in the comments only

Tap on a block to expand it, and tap it again to revert.

Cassette, Electron
Docked, 6502SP, Master
   A                    The item number of the piece of equipment (0-11) as
                        shown in the table at PRXS

   A                    The item number of the piece of equipment (0-13) as
                        shown in the table at PRXS




 Returns:

   (Y X)                The item price in Cr * 10 (Y = high byte, X = low byte)



 Other entry points:

   prx-3                Return the price of the item with number A - 1

   c                    Contains an RTS



 SEC                    \ Decrement A (for when this routine is called via
 SBC #1                 \ prx-3)

.prx

 ASL A                  \ Set Y = A * 2, so it can act as an index into the
 TAY                    \ PRXS table, which has two bytes per entry

 LDX PRXS,Y             \ Fetch the low byte of the price into X

 LDA PRXS+1,Y           \ Fetch the high byte of the price into A and transfer
 TAY                    \ it to X, so the price is now in (Y X)

.c

 RTS                    \ Return from the subroutine