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In computer programming, Base64 (also known as tetrasexagesimal) is a group of binary-to-text encoding schemes that transforms binary data into a sequence of printable characters, limited to a set of 64 unique characters. More specifically, the source binary data is taken 6 bits at a time, then this group of 6 bits is mapped to one of 64 unique ...
A binary-to-text encoding is encoding of data in plain text.More precisely, it is an encoding of binary data in a sequence of printable characters.These encodings are necessary for transmission of data when the communication channel does not allow binary data (such as email or NNTP) or is not 8-bit clean.
If the data is Base64-encoded, then the data part may contain only valid Base64 characters. [7] Note that Base64-encoded data: URIs use the standard Base64 character set (with '+' and '/' as characters 62 and 63) rather than the so-called "URL-safe Base64" character set. Examples of data URIs showing most of the features are:
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:
In caret notation the null character is ^@. On some keyboards, one can enter a null character by holding down Ctrl and pressing @ (on US layouts just Ctrl+2 will often work, there being no need for ⇧ Shift to get the @ sign). The hexadecimal notation for null is 00. Decoding the Base64 string AA== also yields the null character.
The resulting string is encoded using a variant of Base64 (+/ and with padding). The authorization method and a space character (e.g. "Basic ") is then prepended to the encoded string. For example, if the browser uses Aladdin as the username and open sesame as the password, then the field's value is the Base64 encoding of Aladdin:open sesame ...
HTML and XML provide ways to reference Unicode characters when the characters themselves either cannot or should not be used. A numeric character reference refers to a character by its Universal Character Set/Unicode code point, and a character entity reference refers to a character by a predefined name. A numeric character reference uses the ...
Multiple valid types (VisibleString, PrintableString, GeneralString, UniversalString, UTF8String) Data specifications SET OF (unordered) and SEQUENCE OF (guaranteed order) User definable type