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 Encoder(ByVal n)
    Encoder = n Xor (n \ 2)
End Function
 
Function Decoder(ByVal n)
    Dim g : g = 0
    Do While n > 0
       g = g Xor n
       n = n \ 2
    Loop
    Decoder = g
End Function
 
' Decimal to Binary
Function Dec2bin(ByVal n, ByVal length)
    Dim i, strbin : strbin = ""
    For i = 1 to 5
        strbin = (n Mod 2) & strbin
        n = n \ 2
    Next
    Dec2Bin = strbin
End Function
 
WScript.StdOut.WriteLine("Binary -> Gray Code -> Binary")
For i = 0 to 31
    encoded = Encoder(i)
    decoded = Decoder(encoded)
    WScript.StdOut.WriteLine(Dec2Bin(i, 5) & " -> " & Dec2Bin(encoded, 5) & " -> " & Dec2Bin(decoded, 5))
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