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Universe: ypl

[BBC Master version]

Name: ypl [Show more] Type: Subroutine Category: Universe Summary: Print the current system name
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: * TT27 calls ypl * cmn calls via ypl-1

Print control code 2 (the current system name).
Other entry points: ypl-1 Contains an RTS
.ypl BIT MJ \ Check the mis-jump flag at MJ, and if bit 7 is set BMI ypl16 \ then we are in witchspace, and witchspace doesn't have \ a system name, so jump to ypl16 to return from the \ subroutine JSR TT62 \ Call TT62 below to swap the three 16-bit seeds in \ QQ2 and QQ15 (before the swap, QQ2 contains the seeds \ for the current system, while QQ15 contains the seeds \ for the selected system) JSR cpl \ Call cpl to print out the system name for the seeds \ in QQ15 (which now contains the seeds for the current \ system) \ Now we fall through into the TT62 subroutine, which \ will swap QQ2 and QQ15 once again, so everything goes \ back into the right place, and the RTS at the end of \ TT62 will return from the subroutine .TT62 LDX #5 \ Set up a counter in X for the three 16-bit seeds we \ want to swap (i.e. 6 bytes) .TT78 LDA QQ15,X \ Swap byte X between QQ2 and QQ15 LDY QQ2,X STA QQ2,X STY QQ15,X DEX \ Decrement the loop counter BPL TT78 \ Loop back for the next byte to swap .ypl16 RTS \ Once all bytes are swapped, return from the \ subroutine