Declaration for C calling C++

#include <stdio.h>

void CPLUSF (int parm);
int  CPLUSF2 (int parm);

int main()  {
  int x,y;

  x=3;
  y=CPLUSF2(x);
  printf("x = %d, y = %d\n",x,y);

  CPLUSF(x);

}

#include <stdio.h>
#include <stdlib.h>
extern "C"  {
  void CPLUSF (int parm);
  int CPLUSF2 (int parm);
}

void CPLUSF (int parm) {

}

int CPLUSF2 (int parm) {
  int myint;
  myint=parm;
  return (myint);
}