Une explication très simple :

The characters "Ow!" will be converted to three 8 bit byte(0x4F, 0x77, 0x21)
These 3 bytes will be transformed to 24 bits(01001111 01110111 00100001)
These 24 bits will be divided into groups of 6 bits(010011、110111、011100、1000001).
Each 6 bits will be a value between 0 and 63, it will map to one of 64 characters above. The end result after encoding is "T3ch".

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