Humans are also regularly harmed by pollution. Long-term exposure to air pollution, for example, can lead to chronic respiratory disease, lung cancer and other diseases. Toxic chemicals that accumulate in top predators can make some species unsafe to eat.
#include <iostream> is the Standard C++ way to include header files, the. 'iostream' is an identifier that maps to the file iostream.h. In older C++ you had to specify the filename of the header file, hence #include. <iostream.h>. Older compilers may not recognise the modern method, newer.
extern ostream cout; Standard output stream. Object of class ostream that represents the standard output stream oriented to narrow characters (of type char). It corresponds to the C stream stdout. The standard output stream is the default destination of characters determined by the environment.