Why use "_U_" instead of simple 'U'?

Hello,

I came across this decleration in one of the header files:

#define RTC_MODE0_INTENSET_CMP0_Pos _U_(8)

The process is clear to me, but being a novice programmer, my question is why one would use "_U_" to declare an unsigned integer instead of standard 'U'.

The other question is: where this "_U_" is declared initially?

Thanks for the help!

_boomer

Any macro starting with an underscore is reserved for the implementation, which is what defines _U_ here.

As for why the implementation uses _U_ instead of U, imagine what would happen if an application also defined something named U (let's just say that bad things could happen).

I can't answer your last question directly, but I can say that _U_ is defined somewhere in the implementation's header files (is this for SAMD? If so, it'll probably be under one of the SAMD compiler include directories).

Thanks christop for explaining.

I am using PIC32CM.

-boomer