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.
 
# Project : Gray code
 
pos = 5
see "0 : 00000 => 00000 => 00000" + nl
for n = 1 to 31
     res1 = tobase(n, 2, pos)
     res2 = tobase(grayencode(n), 2, pos)
     res3 = tobase(graydecode(n), 2, pos)
     see "" + n + " : " + res1 + " => " + res2 +  " => " + res3 + nl
next
 
func grayencode(n)
        return n ^ (n >> 1)
 
func graydecode(n)
        p = n
        while (n = n >> 1) 
                  p = p ^ n
        end
        return p
 
func tobase(nr, base, pos) 
        binary = 0
        i = 1  
       while(nr != 0) 
              remainder = nr % base
              nr = floor(nr/base)
              binary= binary + (remainder*i)
              i = i*10
       end
       result = ""
       for nr = 1 to  pos - len(string(binary))
             result = result + "0" 
       next
       result = result + string(binary)
       return result
 