Thank you very much. I keep improving my knowledge. A question.

The hash algorithm seems to be a command in the software or programming language being used, right. Is this algorithm always the same? If you hash the same document with Java and with Linux , for example: will you get the same hash, the same digital signature, de same number? On the other hand: who programs this has? The programmer that programmed the hash seems to have an advantage here, or not?