But there are also procedures in which the order of steps is unimportant. Often in such procedures, a conventional orderemerges to avoid confusion. An excellent example in the U.S. context is addressing letters for mailing. Every school child knows that you do it in this order:First name Last nameHouse NumberStreet nameCity, State Zip code CountryOddly enough, this conventional order is exactly the reverse of how the address is examined at the various postal distribution points in the mail system. The post office at the point of origin would look at the country and put the letter in a pile for international mail. The distribution center in the destination country would look at the zip code and perhaps state. The local post office would examine the street address and place it in the proper mail carrier's route, and the mail carrier, upon arriving on that street, would place it into the mailbox bearing that address. Finally, whoever checked the mail at the house would look at the name and givesthe letter to the person it was addressed to. In some countries the conventional order follows the logical task order in addressing envelopes. In Russia, for example, letters are addressed in exactly the opposite order to the U.S. convention.Example: You want to clear your screen of all buttons and fields, show a field with text, and wait for the user to click, then hide the field and show the former ones.To work correctly, not only do all the commands have to be there, they have to be in the right order.