 conversion between the two-wire transmission link and the four-wire telephone set, separating the incoming audio from the out- going signal. Coding Schemes: ASCII, EBCDIC, Unicode, and Beyond A coding scheme (or collating sequence) is a pattern of bits used to represent the characters in a character set, as well as carriage returns and other keyboard or con- Data Flow trol functions. Over time, different computer manufacturers and consortiums have introduced different coding schemes. The most commonly used coding schemes are ASCII, EBCDIC, and Unicode. The American Standard Code for Information Interchange (ASCII) is probably the most familiar coding scheme. ASCII has seven information bits per character, and it has one additional bit that's a control bit, called a parity bit, used for error detection. In ASCII, seven ones or zeros are bundled together to represent each character. A total of 128 characters (i.e., 27, for the seven bits of information per character and the two possible values of each character) can be represented in ASCII coding. At about the same time that the whole world agreed on ASCII as a common coding scheme, IBM introduced its own proprietary scheme, called Extended Binary Coded Decimal Interchange Code (EBCDIC). EBCDIC involves eight bits of infor- mation per character and no control bits. Therefore, you can represent 256 possible characters (i.e., 28) with EBCDIC. This sounds like a lot of characters, but it's not enough to handle all the characters needed in the languages throughout the world. Complex Asian languages, for instance, can include up to 60,000 characters. In Table 5.3, you can see that the uppercase letter A in ASCII coding looks quite different than it does in EBCDIC. This could be a source of incompatibility. If your workstation is coded in ASCII and you're trying to communicate with a host that's looking for EBCDIC, you will end up with garbage on your screen because your machine will not be able to understand the alphabet that the host is using. In the mid-1980s, a codi