Gray code
Karnaugh maps
Create functions to encode a number to and decode a number from Gray code.

Display the normal binary representations, Gray code representations, and decoded Gray code values for all 5-bit binary numbers (0-31 inclusive, leading 0's not necessary).

There are many possible Gray codes. The following encodes what is called "binary reflected Gray code."

Encoding (MSB is bit 0, b is binary, g is Gray code):

if b[i-1] = 1
   g[i] = not b[i]
else
   g[i] = b[i]
Or:

g = b xor (b logically right shifted 1 time)
Decoding (MSB is bit 0, b is binary, g is Gray code):

b[0] = g[0]

for other bits:
b[i] = g[i] xor b[i-1]
Reference
 Converting Between Gray and Binary Codes. It includes step-by-step animations.
function gray_encode(integer n)
    return xor_bits(n,floor(n/2))
end function
 
function gray_decode(integer n)
    integer g
    g = 0
    while n > 0 do
        g = xor_bits(g,n)
        n = floor(n/2)
    end while
    return g
end function
 
function dcb(integer n)
    atom d,m
    d = 0
    m = 1
    while n do
        d += remainder(n,2)*m
        n = floor(n/2)
        m *= 10
    end while
    return d
end function
 
integer j
for i = #0 to #1F do
    printf(1,"%05d => ",dcb(i))
    j = gray_encode(i)
    printf(1,"%05d => ",dcb(j))
    j = gray_decode(j)
    printf(1,"%05d\n",dcb(j))
end for