Copy protection: David23

       Name: David23                                                 [Show more]
       Type: Variable
   Category: Copy protection
    Summary: Address pointer to the start of the 6502 stack
    Context: See this variable in context in the source code
 Variations: See code variations for this variable in the different versions
 References: This variable is used as follows:
             * Elite loader (Part 4 of 6) uses David23


 This two-byte address points to the start of the 6502 stack, which descends
 from the end of page 2, less LEN bytes, which comes out as &01DF. So when we
 push 33 bytes onto the stack (LEN being 33), this address will point to the
 start of those bytes, which means we can push executable code onto the stack
 and run it by calling this address with a JMP (David23) instruction. Sneaky
 stuff!


.David23

 EQUW (512-LEN)         \ The address of LEN bytes before the start of the stack