Index: external.c
===================================================================
--- external.c	(revision 14)
+++ external.c	(working copy)
@@ -23,13 +23,15 @@
 char *ext_mode = NULL;
 
 static c_int ext_word[PLAINTEXT_BUFFER_SIZE];
+static c_int ext_word_chksum;
 
-static struct c_ident ext_globals = {
-	NULL,
-	"word",
-	ext_word
+static struct c_ident ext_globals[] = { 
+{ NULL, "word", ext_word },
+{ NULL, "_chksum", &ext_word_chksum },
+{ NULL, NULL, NULL },
 };
 
+
 static struct c_ident *f_generate;
 struct c_ident *f_filter;
 
@@ -58,12 +60,22 @@
 
 void ext_init(char *mode)
 {
+	int idx_ext_globals = 0;
+
 	if (!(ext_source = cfg_get_list(SECTION_EXT, mode))) {
 		fprintf(stderr, "Unknown external mode: %s\n", mode);
 		error();
 	}
 
-	if (c_compile(ext_getchar, ext_rewind, &ext_globals)) {
+	/* initialize globals linked list from the ext_globals array */
+        while (ext_globals[ idx_ext_globals ].name != NULL) {
+	  ext_globals[ idx_ext_globals ].next = 
+	    &ext_globals[ idx_ext_globals + 1 ];
+	  ++idx_ext_globals;
+	}
+	  
+
+	if (c_compile(ext_getchar, ext_rewind, &ext_globals[0] )) {
 		if (!ext_line) ext_line = ext_source->tail;
 
 		fprintf(stderr, "Compiler error in %s at line %d: %s\n",
@@ -76,6 +88,7 @@
 	c_execute(c_lookup("init"));
 
 	f_generate = c_lookup("generate");
+	/* otheus: presumably, user's generate() can make its own chksum */
 	f_filter = c_lookup("filter");
 
 	ext_mode = mode;
@@ -88,8 +101,11 @@
 
 	internal = (unsigned char *)in;
 	external = ext_word;
-	while (*internal)
+	ext_word_chksum = 0;	  /* initialize chksum every time */
+	while (*internal) {
+		ext_word_chksum += ( *internal % 256 );	/* compute chksum */
 		*external++ = *internal++;
+	}
 	*external = 0;
 
 	c_execute(f_filter);