what does this mean?

int code = 0;
code | = 0x01;

Answer 1, authority 100%

shouldn’t be a problem with the first line. And the second is just

code = code | 0x01;

That is, the usual bitwise or.

0x01 is this form for writing hexadecimal numbers. In this case, it’s just 1. 0xFF is already 255.