Assign a non-Number to a Double Variable?

I am writing a math program, using variables of type double, and had initialized all variables to 0.0.

I now realize that not all results will be valid.

Is there a way to explicitly assign a variable of type double a non-numeric value, for example, "NaN", "Undefined", or "Unassigned" or something like that?

That way, when I read through the printout of results, I will realize the "NaN" results indicate a valid solution was not found. Whereas a 0.0 might not stand out.

I'd hate to have to go back and delete the initialization, and then re-assign 998 values just for the sake of 2 non-solutions.

Can this be done?
Thanks for the information. Sounds easy enough.

So, to assign this value to a variable, I assume it is as simple as the following example:

 ``123456789101112`` ``````double a, b, c; a = 3.14158; b = 0.0; if (b != 0){ c = a/b; } else { cout << "Attempted divide by zero.\n"; c = std::numeric_limits::quiet_NaN(); }``````

Is this feature part of the C++ standard, or is it specific to Microsoft? I would like my code to be as close to standards as possible.
The above is standard C++. http://www.cplusplus.com/reference/limits/numeric_limits/. I've tested the quiet_NAN with g++
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