text: #include <stdio.h>
  #define SWAP(a,b) ftemp=(a);(a)=(b);(b)=ftemp
  
  void fourew(FILE *file[5], int *na, int *nb, int *nc, int *nd)
  {
  	int i;
  	FILE *ftemp;
  
  	for (i=1;i<=4;i++) rewind(file[i]);
  	SWAP(file[2],file[4]);
  	SWAP(file[1],file[3]);
  	*na=3;
  	*nb=4;
  	*nc=1;
  	*nd=2;
  }
  #undef SWAP
  /* (C) Copr. 1986-92 Numerical Recipes Software 9.1-5i. */
  