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All C++ standard library names, including the C library names,
if you include them, are defined in the namespace std
using
the following C++ syntax:
#include <cstdlib> // instead of stdlib.h
This means that you must qualify all the library names using one of the following methods:
Specify the standard namespace, for example:
std::printf("example\n");
Use the C++ keyword using to import a name to the global namespace:
using namespace std; printf("example\n");
Note
errno
is a macro, so it is not necessary
to qualify it with a namespace.