A file format using 64 ASCII characters to encode the six bit binary data values 0-63.To convert data to base 64, the first byte is placed in the most significant eight bits of a 24-bit buffer, the next in the middle eight, and the third in the least significant eight bits.If there a fewer than three bytes to encode, the corresponding buffer bits will be zero.The buffer is then used, six bits at a time, most significant first, as indices into the string "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" and the indicated character output.If there were only one or two input bytes, the output is padded with two or one "=" characters respectively.This prevents extra bits being added to the reconstructed data.The process then repeats on the remaining input data.Base 64 is used when transmitting binary data through text-only media such as electronic mail, and has largely replaced the older uuencode encoding.(2004-07-17)