diff --git a/compiler/libpc300/sc2.c b/compiler/libpc300/sc2.c
index 5f7839d5..283a25f1 100755
--- a/compiler/libpc300/sc2.c
+++ b/compiler/libpc300/sc2.c
@@ -1270,7 +1270,7 @@ static int command(void)
       } /* while */
       end=lptr;
       /* check pattern to match */
-      if (!isalpha(*start) && *start!='_') {
+	  if (!alpha(*start)) {
         error(74);      /* pattern must start with an alphabetic character */
         break;
       } /* if */
@@ -1321,7 +1321,7 @@ static int command(void)
       } /* while */
       substitution[count]='\0';
       /* check whether the definition already exists */
-      for (prefixlen=0,start=(unsigned char*)pattern; isalpha(*start) || isdigit(*start) || *start=='_'; prefixlen++,start++)
+      for (prefixlen=0,start=(unsigned char*)pattern; alphanum(*start); prefixlen++,start++)
         /* nothing */;
       assert(prefixlen>0);
       if ((def=find_subst(pattern,prefixlen))!=NULL) {
@@ -1485,7 +1485,7 @@ static int substpattern(unsigned char *line,size_t buffersize,char *pattern,char
   memset(args,0,sizeof args);
 
   /* check the length of the prefix */
-  for (prefixlen=0,s=(unsigned char*)pattern; isalpha(*s) || isdigit(*s) || *s=='_'; prefixlen++,s++)
+  for (prefixlen=0,s=(unsigned char*)pattern; alphanum(*s); prefixlen++,s++)
     /* nothing */;
   assert(prefixlen>0);
   assert(strncmp((char*)line,pattern,prefixlen)==0);
@@ -1645,7 +1645,7 @@ static void substallpatterns(unsigned char *line,int buffersize)
     /* find the start of a prefix (skip all non-alphabetic characters),
      * also skip strings
      */
-    while (!isalpha(*start) && *start!='_' && *start!='\0') {
+    while (!alpha(*start) && *start!='\0') {
       /* skip strings */
       if (is_startstring(start)) {
         start=(unsigned char *)skipstring(start);
@@ -1663,7 +1663,7 @@ static void substallpatterns(unsigned char *line,int buffersize)
       while ((*start<=' ' && *start!='\0') || *start=='(')
         start++;
       /* skip the symbol behind it */
-      while (isalpha(*start) || isdigit(*start) || *start=='_')
+	  while (alphanum(*start))
         start++;
       /* drop back into the main loop */
       continue;
@@ -1671,7 +1671,7 @@ static void substallpatterns(unsigned char *line,int buffersize)
     /* get the prefix (length), look for a matching definition */
     prefixlen=0;
     end=start;
-    while (isalpha(*end) || isdigit(*end) || *end=='_') {
+	while (alphanum(*end)) {
       prefixlen++;
       end++;
     } /* while */
@@ -2512,7 +2512,7 @@ SC_FUNC void delete_symbols(symbol *root,int level,int delete_labels,int delete_
       /* for user defined operators, also remove the "prototyped" flag, as
        * user-defined operators *must* be declared before use
        */
-      if (sym->ident==iFUNCTN && !isalpha(*sym->name) && *sym->name!='_' && *sym->name!=PUBLIC_CHAR)
+      if (sym->ident==iFUNCTN && !alpha(*sym->name))
         sym->usage &= ~uPROTOTYPED;
       root=sym;                 /* skip the symbol */
     } /* if */
diff --git a/compiler/libpc300/sclist.c b/compiler/libpc300/sclist.c
index 147ada14..57c82702 100755
--- a/compiler/libpc300/sclist.c
+++ b/compiler/libpc300/sclist.c
@@ -255,16 +255,16 @@ SC_FUNC void delete_pathtable(void)
 
 static stringpair substpair = { NULL, NULL, NULL};  /* list of substitution pairs */
 
-static stringpair *substindex['z'-'A'+1]; /* quick index to first character */
+static stringpair *substindex['z'-PUBLIC_CHAR+1]; /* quick index to first character */
 static void adjustindex(char c)
 {
   stringpair *cur;
-  assert(c>='A' && c<='Z' || c>='a' && c<='z' || c=='_');
-  assert('A'<'_' && '_'<'z');
+  assert(c>='A' && c<='Z' || c>='a' && c<='z' || c=='_' || c==PUBLIC_CHAR);
+  assert(PUBLIC_CHAR<'A' && 'A'<'_' && '_'<'z');
 
   for (cur=substpair.next; cur!=NULL && cur->first[0]!=c; cur=cur->next)
     /* nothing */;
-  substindex[(int)c-'A']=cur;
+  substindex[(int)c-PUBLIC_CHAR]=cur;
 }
 
 SC_FUNC stringpair *insert_subst(char *pattern,char *substitution,int prefixlen)
@@ -304,8 +304,8 @@ SC_FUNC stringpair *find_subst(char *name,int length)
   stringpair *item;
   assert(name!=NULL);
   assert(length>0);
-  assert(*name>='A' && *name<='Z' || *name>='a' && *name<='z' || *name=='_');
-  item=substindex[(int)*name-'A'];
+  assert(*name>='A' && *name<='Z' || *name>='a' && *name<='z' || *name=='_' || *name==PUBLIC_CHAR);
+  item=substindex[(int)*name-PUBLIC_CHAR];
   if (item!=NULL)
     item=find_stringpair(item,name,length);
 
@@ -334,8 +334,8 @@ SC_FUNC int delete_subst(char *name,int length)
   stringpair *item;
   assert(name!=NULL);
   assert(length>0);
-  assert(*name>='A' && *name<='Z' || *name>='a' && *name<='z' || *name=='_');
-  item=substindex[(int)*name-'A'];
+  assert(*name>='A' && *name<='Z' || *name>='a' && *name<='z' || *name=='_' || *name==PUBLIC_CHAR);
+  item=substindex[(int)*name-PUBLIC_CHAR];
   if (item!=NULL)
     item=find_stringpair(item,name,length);
   if (item==NULL)