EBCDIC, ASCII, and Unicode are character sets that determine how letters, numbers, and other characters are represented by bits. z/OS systems work with EBCDIC code. Only HFS and zFS file systems used with Unix System Services (USS) make it possible to save data in both ASCII and EBCDIC. When exchanging data between z/OS systems and systems using ASCII or Unicode (including from USS to z/OS, for example), there is a risk that information could be corrupted if incorrect translation tables (code page translation) are used. Here, the translation of special characters is a particularly frequent problem.