Different countries use different keyboard layouts. System software interprets the internal codes of the keys, assigning the appropriate codes of the current code page to them. And the code page, and keyboard layout is determined by the operating system settings. For example, the German keyboard has several accented characters, such as a and b. The French keyboard lacks brackets. The Greek keyboard as well as Ukrainian one allows for switch between English and Greek character sets. The Scandinavian alphabet has specific characters that are absent in the most popular West European code page 850 character set. Localization testing services help software developers to adapt their products to culture of other countries where they are going to sell these products. The services are used to detect spelling mistakes in the product and make sure that it is well adapted for foreign market.
Some keyboards have another key, performing the function of <Shift> key, and it is marked as <Alt-Gr>. It allows you to enter the third character drawn on the alphanumeric key.
In addition, non-US keyboards support so-called dead keys. These keys are used for typing accented characters. They do not perform any actions, until the user presses the next key, then corresponding accented character appears on the screen.
And one more thing: the program should provide the user with access to the symbols that are not on the keyboard (otherwise how the Italian will be able to address a letter to his German counterpart?). Make sure that the program allows you not only to insert these characters into the text (for example, by copying them from another application) but also displays them properly. If you want to know more about localization testing and software development, in general, please, turn to trusted QA consultants for help.
To conduct the testing successfully you need to try out the program, working on that keyboard and with that system software which will be exploited by the users.
For example, the program can only allow English letters to be entered in a specific field, rejecting all other symbols and control codes entered by the user. Thus, the app ensures that English-speaking user will be unable to enter nothing but text in this field, but such a limitation is unacceptable for users of other national alphabets.
Since these restrictions are implemented in software, you will have to test every text field, checking how the program receives and displays all the extended characters, of course, where entry of these characters is allowed. It is reasonable to recruit employees of software testing companies in USA in order to cost effectively improve the quality of the product and accelerate its launch.