; link with PIOxxx.OBJ

        sectiondata

output:         db " : "
inbinary:       db "00000 => "
graybinary:     db "00000 => "
outbinary:      db "00000"
                db 13,10,0        ; carriage return and null terminator

        sectioncode

start!
        gosub initplatform

        beginfunc
        localvar i.d,g.d,b.d

        i=0
        whileless i,32
        callex g,gray_encode,i
        callex b,gray_decode,g

        callex ,bin2string,i,inbinary,5              ; 5 = number of binary digits
        callex ,bin2string,g,graybinary,5
        callex ,bin2string,b,outbinary,5

        callex ,printhex8,i                  ; display hex value
                                             ; because there is no PIO routine for decimals...
        callex ,printnt,output.a

        i=_+1
        wend

        endfunc
        end

gray_encode:
        beginfunc n.d
        n=_ xor (n shr 1)
        endfunc n
        returnex 4                           ; clean off 1 parameter from the stack

gray_decode:
        beginfunc n.d
        localvar p.d
        p=n
        whilegreater n,1
        n=_ shr 1 > p=_ xor n
        wend
        endfunc p
        returnex 4                           ; clean off 1 parameter from the stack

bin2string:
        beginfunc digits.d,straddr.d,value.d

        whilegreater digits,0
        digits=_-1
        [straddr].b=value shr digits and 1+$30        ; write an ASCII '0' or '1'
        straddr=_+1                                   ; increment the pointer
        wend

        endfunc
        returnex $0C                         ; clean off 3 parameters from the stack