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 Encode(v : Integer) : Integer;
begin
   Result := v xor (v shr 1);
end;
 
function Decode(v : Integer) : Integer;
begin
   Result := 0;
   while v>0 do begin
      Result := Result xor v;
	  v := v shr 1;
   end;
end;
 
PrintLn('decimal  binary   gray    decoded');
 
var i : Integer;
for i:=0 to 31 do begin
   var g := Encode(i);
   var d := Decode(g);
   PrintLn(Format('  %2d     %s   %s   %s  %2d',
                  [i, IntToBin(i, 5), IntToBin(g, 5), IntToBin(d, 5), d]));
end;