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A file format using 64 ASCIIcharacters to encode the six bit binary data values 0-63.To convert data to base 64, the first byte is placed in themost significant eight bits of a 24-bit buffer, the next inthe middle eight, and the third in the least significant eightbits. If there a fewer than three bytes to encode, thecorresponding buffer bits will be zero. The buffer is thenused, six bits at a time, most significant first, as indicesinto the string"ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/"and the indicated character output. If there were only one ortwo input bytes, the output is padded with two or one "="characters respectively. This prevents extra bits being addedto the reconstructed data. The process then repeats on theremaining input data.Base 64 is used when transmitting binary data throughtext-only media such as electronic mail, and has largelyreplaced the older uuencode encoding.