I'm afraid you will need to give more information. What field is this equation from? What do "HMAC" and "SHA1" mean? Ox5c5c and Ox3636 are probably octal numbers. Is this a computer problem and "HMAC" is the data in an accumulator? "SHA1" might be a shift operation on a computer register. In that case, I would expect "//" to be a binary operation, perhaps an "OR" operation.