2.9BSD - /usr/src/cmd/struct/b.h

   1: extern int xxindent, xxval, newflag, xxmaxchars, xxbpertab;
   2: extern int xxlineno;        /* # of lines already output */
   3: #define xxtop   100     /* max size of xxstack */
   4: extern int xxstind, xxstack[xxtop], xxlablast, xxt;
   5: struct node
   6:     {int op;
   7:     char *lit;
   8:     struct node *left;
   9:     struct node *right;
  10:     };

Defined struct's

Defined macros

Usage of this include