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Because Base64 is a six-bit encoding, and because the decoded values are divided into 8-bit octets, every four characters of Base64-encoded text (4 sextets = 4 × 6 = 24 bits) represents three octets of unencoded text or data (3 octets = 3 × 8 = 24 bits). This means that when the length of the unencoded input is not a multiple of three, the ...
The 95 isprint codes 32 to 126 are known as the ASCII printable characters. Some older and today uncommon formats include BOO, BTOA , and USR encoding. Most of these encodings generate text containing only a subset of all ASCII printable characters: for example, the base64 encoding generates text that only contains upper case and lower case ...
However if a UTF-7 translator is to/from UTF-16 then it can (and probably does) [citation needed] encode each surrogate half as though it was a 16-bit code point, and thus can encode all code points. It is unclear if other UTF-7 software (such as translators to UTF-32 or UTF-8) support this.
The use of UTF-32 under quoted-printable is highly impractical, but if implemented, will result in 8–12 bytes per code point (about 10 bytes in average), namely for BMP, each code point will occupy exactly 6 bytes more than the same code in quoted-printable/UTF-16. Base64/UTF-32 gets 5 + 1 ⁄ 3 bytes for any code point.
In the table below, the column "ISO 8859-1" shows how the file signature appears when interpreted as text in the common ISO 8859-1 encoding, with unprintable characters represented as the control code abbreviation or symbol, or codepage 1252 character where available, or a box otherwise. In some cases the space character is shown as ␠.
More common today is the Base64 format, which is based on the same concept of alphanumeric-only as opposed to ASCII 32–95. All three formats use 6 bits (64 different characters) to represent their input data. Base64 can also be generated by the uuencode program and is similar in format, except for the actual character translation:
Quoted-Printable, or QP encoding, is a binary-to-text encoding system using printable ASCII characters (alphanumeric and the equals sign =) to transmit 8-bit data over a 7-bit data path or, generally, over a medium which is not 8-bit clean.
In basic HTTP authentication, a request contains a header field in the form of Authorization: Basic <credentials>, where <credentials> is the Base64 encoding of ID and password joined by a single colon :. It was originally implemented by Ari Luotonen at CERN in 1993 [1] and defined in the HTTP 1.0 specification in 1996. [2]