Character encoding schemes

Since computers have been around they have been used to store text, but as computers only operate in ones and zeros, text can not be represented directly. Rather a character encoding scheme is used which maps internal computer numbers to characters. So long as the same convention... 

Ever since computers have been around they have been used to store text, but as computers operate only in ones and zeros, text cannot be represented directly. Rather a character-encoding scheme is used, which maps internal computer niunbers onto characters. So long as the same convention is maintained by the readers and writers, chunks of memory can be used to represent encoded text. The issue for a TTS system is to identify the character encoding being used and process it appropriately. Partly due to the sheer diversity of the world s writing systems and partly due to historical issues in the development of character-encoding schemes, there are several ways in which characters can be encoded. 

The ASCII is a character-encoding scheme based on the ordering of the English alphabet. ASCII codes represent text in computers, communications equipment, and other devices that use text. ASCII includes definitions for 128 characters 33 are nonprinting control characters that affect how text and space is processed, 94 are printable characters, and the space character is considered an invisible graphic. For example, the ASCII code for the letter A is 65 and for the letter a is 97. 

Unicode simply defines a number for each character, it is not an encoding scheme in itself For this, a number of different schemes have been proposed. UTF-8 is popular on Unix machines and on the internet. Is is a variably width encoding, meaning that normal ascii remains unchanged but that wider character formats are used when necessary. By contrast UTF-16 popular in Microsoft products, uses a fixed size 2 byte format. More recent extensions to Unicode mean that the original 16 bit limitation has been surpassed, but this in itself is not a problem (specifically for encodings such as UTF-8 which are extensible). 

Having a platform-independent encoding for data transport does not yet mean that it is possible to transport the data unchanged via a given Internet channel. If sent, for example, as part of an electronic mail message, only 7-bit characters and short lines up to 80 characters can safely be expected to survive all possible involved transport steps. Hence there is a demand to encode and decode binary or 8-bit information into more robust forms. The most commonly used and unfortunately incompatible schemes for this task are the uuencode, mac-binhex, base64, and quoted-printable encodings for MIME applications, and UTF-8 for UNICODE. ... 

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