How does CRC work?

Chapter 1  Introduction

Chapter 1.1 Introduction
Everybody read prompt „CRC error…and anything else”. When you will finish this course you will know what is this about!

Chapter 1.2 How does come  in and walk out of the every animation?
The animation is the main advantage of this article. The interpretation is very easy then and the added text will be not necessary probably! Animation is based on the Scratch language. You don’t need to know and install it!
I recommend to turn on the audio in the computer. It isn’t necessary but it is very helpfull.
Additional Scratch requirement:
– Classical computers and laptops only. No mobiles and tablets!
– Adobe FlashPlayer. Everybody almost has it.
You call animation by clicking the text animation located under the majority of the figures–>see Note. You come to appropriate SCRATCH server site then, but you leave this article site simultaneously! So you need to return to the article when you will finish the animationYou do it by clicking the classical windows „return to previous site” push-button with the arrow–>see Fig. 1-1.
And my friendly advice. Don’t click clock-zegar too quickly! Give system the chance to react!
 When you click  animation–>Scratch may ask you to click „Adobe Flash Player” symbol! Do it of course.

Fig. 1-1
How does return to the article from the animation?

Chapter 1.3 Transmission without CRC
That is without error checking. The subject is so easy that consider it as a occasion to bring  into contact with the animation.

Fig. 1-2
Transmission without CRC  ANIMATION
AIR-Appropriate Information Register is located in Warsaw and RR-Receiver Register in London, for example.  Every clock („zegar”) pulse  pushes 1 digit from AIR to RR.  The „clouds” with the statement in every system state ease the understanding.

Chapter 1.4 Transmission with CRC – i.e with errors checking
We observe AIR and RR simultaneously and  we know that the transmission is ok!  But electromagnetics disturbance can change the 2-nd digit and the receiver register is  RR=38547 instead of 3254 for example! The CRC method enables the RR-Receiver Register to know that there are transmission errors probably. You will know more in the next chapter.  Why is the name  AIR-Appropriate Information Register instead of TR-Transmission Register simply? You will know it also.

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