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.
      INSTALL @lib$+"STRINGLIB"
 
      PRINT "   Decimal    Binary      Gray   Decoded"
      FOR number% = 0 TO 31
        gray% = FNgrayencode(number%)
        PRINT number% "     " FN_tobase(number%, 2, 5) ;
        PRINT "     " FN_tobase(gray%, 2, 5) FNgraydecode(gray%)
      NEXT
      END
 
      DEF FNgrayencode(B%) = B% EOR (B% >>> 1)
 
      DEF FNgraydecode(G%) : LOCAL B%
      REPEAT B% EOR= G% : G% = G% >>> 1 : UNTIL G% = 0
      = B%