To convert from standard binary to Gray code you need to be familiar with the logical XOR operator (eXclusive OR). The XOR operator outputs a 1 bit if either of two input bits is 1, but not both. The truth table for all possible inputs p and q is as follows:

p q output

0 0 0

0 1 1

1 0 1

1 1 0

Armed with this knowledge, we can convert from standard binary code to Gray code using the following algorithm:

Step 1: Fix the most-significant bit, MSB, which is always the same for both. If there is only one bit, then we're done. Otherwise proceed to step 2.

Step 2: XOR the first two bits of the binary code to get the next Gray bit.

Step 3: Discard the first bit of the binary code.

Step 4: If there are two or more bits left in the binary code, goto step 2, otherwise we're done.

Example: Binary = 11001010

(Fix MSB) = 11001010

(1 XOR 1 = 0) 001010

(1 XOR 0 = 1) 01010

(0 XOR 0 = 0) 1010

(0 XOR 1 = 1) 010

(1 XOR 0 = 1) 10

(0 XOR 1 = 1) 0

(1 XOR 0 = 1)

Thus: Gray = 10101111

Note that we XOR pairs of bits in the binary code from left to right until there are no pairs left. The bold bits are the fixed Gray bits reading from top to bottom.

To reverse the process, we need another algorithm, but we still use XOR:

Step 1: Fix the most-significant bit, MSB, which is always the same for both. If there is only one bit, then we're done. Otherwise proceed to step 2.

Step 2: XOR the binary bit we just set with the next Gray bit to fix the next binary bit.

Step 3: If there are more Gray bits, repeat step 2, otherwise we're done.

Example: Gray = 10101111

(Fix MSB) = 10101111

1 XOR 0 = 1

1 XOR 1 = 0

0 XOR 0 = 0

0 XOR 1 = 1

1 XOR 1 = 0

0 XOR 1 = 1

1 XOR 1 = 0

Thus: Binary= 11001010

Note that we carry the fixed bit (in bold) from the previous line into the next line and XOR with the next Gray bit to get the next fixed bit. The bold bits are the fixed binary bits read from top to bottom. We could also write this out as follows, reading left to right:

Gray = 10101111

Binary = 1 XOR 0 = 1 XOR 1 = 0 XOR 0 = 0 XOR 1 = 1 XOR 1 = 0 XOR 1 = 1 XOR 1 = 0

Previous Answer:

[Edit: The previous answer uses arithmetic ADD rather than logical XOR. Apart from anything else, it makes no logical sense for 1 ADD 1 = 0 (it is actually 10 binary, or decimal 2). But so long as you only consider the LSB (least-significant bit) the result will be the same. However 1 XOR 1 is always 0 and is therefore more efficient.]

How do you convert binary to Gray code?

Very Simple Example: Convert natural binary 11001010 to gray code.

Step 1) Copy most significant bit (on very left)

Answer: 1

Step 2) Add from left to right bit by bit of your binary number:

(1+1) 001010 [1+1 = 0]

Answer: 10

Step 3) Continue:

1(1+0)01010

Answer: 101

-------------------------

11(0+0)1010

Answer: 1010

------------------------

110(0+1)010

Answer: 10101

-------------------------

until you get to the end

110010(1+0)

Answer: 10101111 <- Answer in Gray Code

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