; ***************************************************
; *** HiLow.68                                    ***
; *** Tests branching instructions of Sim68k      ***
; *** Tests BRA, BEQ, BGE, CMP, TST               ***
; *** Also uses MOVE, ADDQ, INP, DSP, DSR and HLT ***
; ***************************************************

; Branching instructions  (and status bits updating)  are  hard
; to verify. Here is a little game that will test some of these
; instructions.  Complete your verification with your own tests.

; This is the High-Low Game.
; Here is what it would look like in Pascal:
;
;    R.W := $FFFF;     { Initializes R (Result)            }
;    C.W := $0000;     { Initializes C (Counter)           }
;    Repeat
;       Readln(D0.B)      { "Random" number to find        }
;    Until (D0.B <> 0);   { D0 must be different from 0    }
;    Read (D1.B);         { Player is guessing a number    }
;                 { Player can enter 0 to exit the game    }
;    While (D1.B <> 0) And (R.W <> 0) Do
;     Begin
;       If (D1.B <> D0.B)
;       then
;          If (D1.B < D0.B)
;          then
;             R.W := $1  { Too low }
;          else
;             R.W := $2  { Too high }
;       else
;          R.W := $0;    { Found! }
;       Writeln (R.W);   { Display the message }
;       Inc(C.W);
;       If R.W <> 0
;       then
;          Read (D1.B)
;     End;
;    Writeln (C.W) { Display the number of guesses }


;    Assembly Language       OpCode  Oper1   Oper2
;                           MSB LSB MSB LSB MSL LSB
;--------------------------------------------------
; Branch to the first instruction
BRA.W  @Repeat             ;

; Declarations
DEF.W  @R,    #$FFFF     ;
DEF.W  @C,    #$0000     ;
DEF.W  @Zero, #$0000     ;
DEF.W  @One,  #$0001     ;
DEF.W  @Two,  #$0002     ;
; Choose a random number not 0
LABEL  @Repeat           ;
    INP.B  D0            ;
    BEQ.W  @Repeat       ;

; Player is guessing a number
    INP.B  D1            ;

LABEL  @While            ;
    TST.B  D1            ;
    BEQ.W  @End          ;
    TST.W  @R            ;
    BEQ.W  @End          ;

; D1 <> D0 ?
    CMP.B  D0, D1        ;
    BEQ.W  @Found        ;
    BRA.W  @TooLow       ;

LABEL  @Found            ;
    MOVE.W @Zero, @R     ;
    BRA.W  @Display      ;

LABEL  @TooLow           ;
    BGE.W  @TooHigh      ;
    MOVE.W @One, @R      ;
    BRA.W  @Display      ;

LABEL  @TooHigh          ;
    MOVE.W @Two, @R      ;
; No need for a branching instruction to @Display...

LABEL  @Display          ;
; Display the message
    DSP.W  @R            ;
; Increment the number of guesses (C)
    ADDQ.W #$1, @C       ;
    TST.W  @R            ;
    BEQ.W  @End          ;
    INP.B  D1            ;

LABEL  @EndWhile         ;
    BRA.W  @While        ;

LABEL  @End              ;
; Display the number of guesses
    DSP.W  @C            ;
    HLT.B                ;