Why the C extern keyword is required to call the C program in C ++

C extern keyword description

==> C and C ++ process function names differently. In C ++, some modifiers are added during function name compilation to differentiate function overloading.

==> For C-compiled function libraries, the extern "C" keyword should be specified when declared and called in C ++, this ensures that C ++ still uses the C method to compile the function name during compilation.

==> C ++ can find the correct C function when linking

==> Extern "C" voidf (int A, char B); --- reference the c Function

==> Extern "C" {# include "cexample. h"} --- reference the c file name

==> Extern "C" INTA; --- reference C global variable