grey code


When I was a kid I read this great book called The Invention of the Wheel, which catalogued dozens of inventions that were not as important as they seemed.

One in particular stood out: the invention of a new numbering system. Our current system is so familiar that it’s hard to imagine why anyone would want to invent another one, but this new system had a big advantage over ours. It was called the Gray Code.

The 10 digits in our number system are arranged so that there is only one digit that changes when you go from one number to the next smaller number. If we’re counting in decimal, for example, 9 goes to 10 and then 1 goes to 2 and we’re back where we started. That wouldn’t work very well if every digit changed whenever you went from one number to the next. Imagine having to multiply numbers where every digit was different!

In the Gray Code, only one bit changes when you go from one number to its immediate neighbor. There are still ten digits, but instead of being arranged 000110111100 like ours, they are arranged 000011110011. It’s easy to prove that with this arrangement there is only one bit change between any two numbers (unless they differ by a multiple of ten). This makes it

It is a system of representing numbers in binary that can be used to make binary numbers more user friendly. A grey code is a code which is such that two successive values differ in only one bit. It minimizes the number of times the bits have to change when counting through the numbers from 0 to 2n-1. The standard binary code represents each number in a series by the binary digits 0 and 1. While this works fine for computers, it does not work well for humans, who have trouble distinguishing between sequences like 00101 and 10100.

In contrast, in a gray code sequence, each successive value differs in only one place. For example, consider the following gray code sequence for n = 3:

000

001

011

010

110

111

101

100

The binary equivalents of these values are 000, 001, 011, 010, 110, 111, 101, 100 respectively. Notice that each successive value differs in only one place from its predecessor. This makes it easy to distinguish between the different values when they are displayed on a series of lights or LEDs.

Grey code is a binary code where each successive value differ in only one bit, as well as when the number overflow at the end of the sequence from 1111 to 0000.

In this project, I will be implementing a 3*3 matrix keypad with a grey code decoder. The matrix keypad will be interfaced with an Arduino Uno and the corresponding output will be displayed on Serial Monitor.

Grey code is a system of binary encoding where successive values differ in only one bit. The reflected binary code was originally designed to prevent spurious output from electromechanical switches. Today, Gray codes are widely used to facilitate error correction in digital communications such as digital terrestrial television and some cable TV systems. In fact, many coding schemes that employ error-correcting codes can be viewed as generalizations of Gray coding.

A binary-reflected Gray code list for n bits can be generated recursively from the list for n 1 bits by reflecting the list (i.e., listing the entries in reverse order), prefixing the entries in the original list with a binary 0, prefixing the entries in the reflected list with a binary 1, and then concatenating the original list with the reversed list. For example, generating the n 2 = 4-bit Gray code from the n 1 = 3-bit Gray code:

000

001

011

010

110

111

101

100

The Grey Code is a numerical code in which consecutive values differ by only one bit. This binary code is used for the reflection of decimal digits. The binary numbers are converted into gray numbers by the exclusive OR operation.

The grey code has been used to simplify the circuitry of computers and digital devices. The gray code always produces a sequence that changes only one bit at a time.

In this article, we will discuss the basics of grey code, its properties and its applications.

We will also be implementing a simple MATLAB program to convert a binary number into its equivalent gray number and vice versa.

What is Binary Code?

A binary sequence is a sequence of bits 0 and 1. A grey code of order n is a binary sequence of length 2n such that each pair of adjacent elements (except the first and last) differs in exactly one bit.

For example, here are two sequences of length 8:

10110010 11111100

The sequences above differ in five positions: 1, 2, 4, 6 and 7. These are all the positions where two adjacent elements differ.

You are given three Strings: begin, target and forbid. The String begin is the initial state of the sequence. The String target is the desired state of the sequence at the end. You must change begin into target without ever passing through any string that is forbidden (forbid contains some forbidden strings). More formally, you must change begin into target with a minimal number of changes such that no intermediate string appears in forbid. If there is no way to perform this transformation, return an empty String instead.

If you have a company of 100 people, that’s 100 lunches a day.

A well-run company tries to make the work you do as similar to the work others do as possible. That way it can be divided among many different people and run with a minimum of co-ordination. One of the most powerful ways of doing this is to ensure that everyone is working on the same version of the truth.

But if you’re going to get 100 lunches delivered every day, you need to create a system in which everyone knows what they need to do by lunchtime. So that requires creating a system in which everyone has agreed on the version of the truth about who wants what for lunch.

Hopefully, you now see how these two problems are very similar. In each case, what you want is a system where everyone can find out what the true state of affairs is at any moment.

The difference between the two problems is that in one case we have lots of time to converge on the truth, but not much bandwidth; in the other case we have lots of bandwidth but not much time. They seem like opposite problems, but they’re actually closely related: they’re both instances of a more general problem called consensus in distributed systems.


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