'14 red LEDs being flashed by two 4511 BCD to seven-segment
        'decoders with their MSBs grounded and the remaining bits
        'being driven from the opposite ends of the parallel outputs
        'of an 8 bit pseudo-random sequence generator.

        'John Fields, 24 July 2005

       
        SCREEN 12
        CLS

        q1 = 0
        q2 = 0
        q3 = 0
        q4 = 0
        q5 = 0
        q6 = 0
        q7 = 0
        q8 = 0
        clk = 0
        n = 1
        x = 160
        s = 4500000

        zero$ = "xxxxxx "
        one$ = " xx    "
        two$ = "xx xx x"
        three$ = "xxxx  x"
        four$ = " xx  xx"
        five$ = "x xx xx"
        six$ = "x xxxxx"
        seven$ = "xxx    "
        eight$ = "xxxxxxx"
        nine$ = "xxxx xx"

        PRINT "Press " + CHR$(34) + "f" + CHR$(34) + " to increase display speed, " + CHR$(34) + "s" + CHR$(34) + " to decrease it, or " + CHR$(34) + "q" + CHR$(34) + " to quit."
        

       
shift:  n = 1
        x = 160
        nor = q1 OR q2 OR q3 OR q4 OR q5 OR q6 OR q7
        IF nor = 0 THEN nor = 1 ELSE nor = 0
       
        tap1 = q3 XOR q5
        tap2 = q6 XOR q8
        tap3 = tap1 XOR tap2
        srin = nor XOR tap3

        q8 = q7
        q7 = q6
        q6 = q5
        q5 = q4
        q4 = q3
        q3 = q2
        q2 = q1
        q1 = srin

        clk = clk + 1
        IF clk = 256 THEN clk = 1
       
        lsd = q1 + (2 * q2) + (4 * q3)
        msd = q6 + (2 * q7) + (4 * q8)

        IF lsd = 0 THEN lsd$ = zero$
        IF lsd = 1 THEN lsd$ = one$
        IF lsd = 2 THEN lsd$ = two$
        IF lsd = 3 THEN lsd$ = three$
        IF lsd = 4 THEN lsd$ = four$
        IF lsd = 5 THEN lsd$ = five$
        IF lsd = 6 THEN lsd$ = six$
        IF lsd = 7 THEN lsd$ = seven$
        IF lsd = 8 THEN lsd$ = eight$
        IF lsd = 9 THEN lsd$ = nine$

        IF msd = 0 THEN msd$ = zero$
        IF msd = 1 THEN msd$ = one$
        IF msd = 2 THEN msd$ = two$
        IF msd = 3 THEN msd$ = three$
        IF msd = 4 THEN msd$ = four$
        IF msd = 5 THEN msd$ = five$
        IF msd = 6 THEN msd$ = six$
        IF msd = 7 THEN msd$ = seven$
        IF msd = 8 THEN msd$ = eight$
        IF msd = 9 THEN msd$ = nine$

        disp$ = lsd$ + msd$
       
        DO WHILE n < 15
        z$ = MID$(disp$, n, 1)
        IF z$ = "x" THEN CIRCLE (x, 240), 10, 4 ELSE PAINT (x, 240), 0, 0
        IF z$ = "x" THEN PAINT (x, 240), 4, 4
        n = n + 1
        x = x + 25
        LOOP
           

        FOR t = 1 TO s: NEXT t
        
        s$ = INKEY$
        IF s$ = "f" THEN s = s - 100000
        IF s$ = "s" THEN s = s + 100000
        IF s$ = "q" THEN END

        IF s <= 0 THEN s = 0

        GOTO shift
        END