Ah, in Spanish I think I knew that as "la prueba del 9" (9's try/9's proof). It was a CRC-like operation. I repeat, I think. I knew that mostly from my grandma,

Ah, in Spanish I think I knew that as "la prueba del 9" (9's try/9's proof). It was a CRC-like operation. I repeat, I think. I knew that mostly from my grandma, and I almost never used it.