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Elite on the BBC Micro

Universe: Ze, Removed [Elite-A, Docked]

Name: Ze, Removed [Show more] Type: Subroutine Category: Universe Summary: Initialise the INWK workspace to a hostile ship Deep dive: Fixing ship positions
Context: See this subroutine in context in the source code References: No direct references to this subroutine in this source file

Specifically, this routine does the following: * Reset the INWK ship workspace * Set the ship to a fair distance away in all axes, in front of us but randomly up or down, left or right * Give the ship a 4% chance of having E.C.M. * Set the ship to hostile, with AI enabled This routine also sets A, X, T1 and the C flag to random values. Note that because this routine uses the value of X returned by DORND, and X contains the value of A returned by the previous call to DORND, this routine does not necessarily set the new ship to a totally random location. See the deep dive on "Fixing ship positions" for details.
\ --- Mod: Original Acornsoft code removed: -----------> \.Ze \ JSR ZINF \ Call ZINF to reset the INWK ship workspace \ JSR DORND \ Set A and X to random numbers \ STA T1 \ Store A in T1 \ AND #%10000000 \ Extract the sign of A and store in x_sign \ STA INWK+2 \ TXA \ Extract the sign of X and store in y_sign \ AND #%10000000 \ STA INWK+5 \ LDA #25 \ Set x_hi = y_hi = z_hi = 25, a fair distance away \ STA INWK+1 \ STA INWK+4 \ STA INWK+7 \ TXA \ Set the C flag if X >= 245 (4% chance) \ CMP #245 \ ROL A \ Set bit 0 of A to the C flag (i.e. there's a 4% \ \ chance of this ship having E.C.M.) \ ORA #%11000000 \ Set bits 6 and 7 of A, so the ship is hostile (bit 6 \ \ and has AI (bit 7) \ STA INWK+32 \ Store A in the AI flag of this ship \ \ Fall through into DORND2 to set A, X and the C flag \ \ randomly \ --- End of removed code ----------------------------->