![]() See also: Delimiter § ASCII armor, and Return-to-libc attack § Protection from return-to-libc attacksīinary-to-text encoding methods are also used as a mechanism for encoding plain text. Many programs perform this conversion to allow for data-transport, such as PGP and GNU Privacy Guard (GPG). ![]() This process is referred to as binary to text encoding. Upon safe arrival at its destination, it is then decoded back to its eight-bit form. ![]() To accomplish this, the data is encoded in some way, such that eight-bit data is encoded into seven-bit ASCII characters (generally using only alphanumeric and punctuation characters-the ASCII printable characters). It is often desirable, however, to be able to send non-textual data through text-based systems, such as when one might attach an image file to an e-mail message. For example, if the value of the eighth bit is not preserved, the program might interpret a byte value above 127 as a flag telling it to perform some function. Many computer programs came to rely on this distinction between seven-bit text and eight-bit binary data, and would not function properly if non-ASCII characters appeared in data that was expected to include only ASCII text. Files that contain machine-executable code and non-textual data typically contain all 256 possible eight-bit byte values. In contrast, most computers store data in memory organized in eight-bit bytes. Systems based on ASCII use seven bits to represent these values digitally. For example, the capital letter A is ASCII character 65, the numeral 2 is ASCII 50, the character } is ASCII 125, and the metacharacter carriage return is ASCII 13. The ASCII text-encoding standard uses 128 unique values (0–127) to represent the alphabetic, numeric, and punctuation characters commonly used in English, plus a selection of control codes which do not represent printable characters. ![]()
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