diff --git a/src/frontend/numparam/numparam.h b/src/frontend/numparam/numparam.h
index f29236549..2d2d9740c 100644
--- a/src/frontend/numparam/numparam.h
+++ b/src/frontend/numparam/numparam.h
@@ -19,8 +19,19 @@ typedef enum {Psp     = '{'} _nPsp;      /* Ps expression */
  * I believe the entry_t should be a union of type but I need more info.
  * ----------------------------------------------------------------- */
 
+#define  NUPA_REAL     'R'
+#define  NUPA_STRING   'S'
+#define  NUPA_POINTER  'P'
+#define  NUPA_SUBCKT   'U'
+#define  NUPA_SPACE    ' '
+#define  NUPA_UNKNOWN  '?'
+#define  NUPA_MODEL    'O'
+
+typedef char nupa_type;
+
+
 typedef struct entry_s {
-    char   tp;         /* type: I)nt R)eal S)tring F)unction M)acro P)ointer */
+    nupa_type tp;      /* type: I)nt R)eal S)tring F)unction M)acro P)ointer */
     char *symbol;
     int  level;                 /* subckt nesting level */
     double vl;                  /* float value if defined */
@@ -52,13 +63,13 @@ typedef struct {                /* the input scanner data structure */
 void initdico(dico_t *);
 int donedico(dico_t *);
 void dico_free_entry(entry_t *);
-bool defsubckt(dico_t *, struct card *, char categ);
+bool defsubckt(dico_t *, struct card *, nupa_type categ);
 int findsubckt(dico_t *, char *s, SPICE_DSTRINGPTR subname);
 bool nupa_substitute(dico_t *, char *s, char *r, bool err);
 bool nupa_assignment(dico_t *, char *s, char mode);
 bool nupa_subcktcall(dico_t *, char *s, char *x, bool err);
 void nupa_subcktexit(dico_t *);
 dico_t *nupa_fetchinstance(void);
-char getidtype(dico_t *, char *s);
+nupa_type getidtype(dico_t *, char *s);
 entry_t *attrib(dico_t *, NGHASHPTR htable, char *t, char op);
 void del_attrib(void *);
diff --git a/src/frontend/numparam/spicenum.c b/src/frontend/numparam/spicenum.c
index 615ff9658..1bba67ffa 100644
--- a/src/frontend/numparam/spicenum.c
+++ b/src/frontend/numparam/spicenum.c
@@ -224,7 +224,7 @@ findsubname(dico_t *dico, SPICE_DSTRINGPTR dstr_p)
                 cadd(&name, upcase(s[j]));
                 j++;
             }
-            found = (getidtype(dico, spice_dstring_value(&name)) == 'U');
+            found = (getidtype(dico, spice_dstring_value(&name)) == NUPA_SUBCKT);
         }
     }
 
@@ -532,9 +532,9 @@ void
 nupa_scan(struct card *card, int is_subckt)
 {
     if (is_subckt)
-        defsubckt(dicoS, card, 'U');
+        defsubckt(dicoS, card, NUPA_SUBCKT);
     else
-        defsubckt(dicoS, card, 'O');
+        defsubckt(dicoS, card, NUPA_MODEL);
 }
 
 
@@ -553,7 +553,7 @@ dump_symbol_table(dico_t *dico, NGHASHPTR htable_p, FILE *fp)
          entry;
          entry = (entry_t *) nghash_enumerateRE(htable_p, &iter))
     {
-        if (entry->tp == 'R') {
+        if (entry->tp == NUPA_REAL) {
             spice_dstring_reinit(& dico->lookup_buf);
             scopy_lower(& dico->lookup_buf, entry->symbol);
             name = spice_dstring_value(& dico->lookup_buf);
@@ -660,7 +660,7 @@ nupa_add_param(char *param_name, double value)
     entry = attrib(dico, htable_p, up_name, 'N');
     if (entry) {
         entry->vl = value;
-        entry->tp = 'R';
+        entry->tp = NUPA_REAL;
         entry->ivl = 0;
         entry->sbbase = NULL;
     }
@@ -687,7 +687,7 @@ nupa_add_inst_param(char *param_name, double value)
     entry = attrib(dico, dico->inst_symbols, up_name, 'N');
     if (entry) {
         entry->vl = value;
-        entry->tp = 'R';
+        entry->tp = NUPA_REAL;
         entry->ivl = 0;
         entry->sbbase = NULL;
     }
diff --git a/src/frontend/numparam/xpressn.c b/src/frontend/numparam/xpressn.c
index e960efa68..f29c0d9de 100644
--- a/src/frontend/numparam/xpressn.c
+++ b/src/frontend/numparam/xpressn.c
@@ -389,7 +389,7 @@ entrynb(dico_t *dico, char *s)
 }
 
 
-char
+nupa_type
 getidtype(dico_t *dico, char *s)
 /* test if identifier s is known. Answer its type, or '?' if not in table */
 {
@@ -398,7 +398,7 @@ getidtype(dico_t *dico, char *s)
     if (entry)
         return entry->tp;
 
-    return '?';
+    return NUPA_UNKNOWN;
 }
 
 
@@ -407,10 +407,10 @@ fetchnumentry(dico_t *dico, char *s, bool *perr)
 {
     entry_t *entry = entrynb(dico, s);
 
-    while (entry && (entry->tp == 'P'))
+    while (entry && (entry->tp == NUPA_POINTER))
         entry = entry->pointer;
 
-    if (entry && (entry->tp == 'R'))
+    if (entry && (entry->tp == NUPA_REAL))
         return entry->vl;
 
     *perr = message(dico, "Undefined number [%s]\n", s);
@@ -430,7 +430,7 @@ attrib(dico_t *dico, NGHASHPTR htable_p, char *t, char op)
 
     entry = (entry_t *) nghash_find(htable_p, t);
     if (entry && (op == 'N') &&
-        (entry->level < dico->stack_depth) && (entry->tp != '?'))
+        (entry->level < dico->stack_depth) && (entry->tp != NUPA_UNKNOWN))
     {
         entry = NULL;
     }
@@ -438,7 +438,7 @@ attrib(dico_t *dico, NGHASHPTR htable_p, char *t, char op)
     if (!entry) {
         entry = TMALLOC(entry_t, 1);
         entry->symbol = strdup(t);
-        entry->tp = '?';      /* signal Unknown */
+        entry->tp = NUPA_UNKNOWN;      /* signal Unknown */
         entry->level = dico->stack_depth;
         nghash_insert(htable_p, t, entry);
     }
@@ -467,7 +467,7 @@ static bool
 nupa_define(dico_t *dico,
        char *t,                 /* identifier to define */
        char op,                 /* option */
-       char tpe,                /* type marker */
+       nupa_type tpe,           /* type marker */
        double z,                /* float value if any */
        int w,                   /* integer value if any */
        char *base)              /* string pointer if any */
@@ -480,7 +480,7 @@ nupa_define(dico_t *dico,
       we already make symbol entries which are dummy globals !
       we mark each id with its subckt level, and warn if write at higher one.
     */
-    char c;
+    nupa_type c;
     bool warn;
     entry_t *entry;             /* spice table entry */
     NGHASHPTR htable_p;         /* hash table */
@@ -496,22 +496,22 @@ nupa_define(dico_t *dico,
     if (!entry)
         return message(dico, " Symbol table overflow\n");
 
-    if (entry->tp == 'P')
+    if (entry->tp == NUPA_POINTER)
         entry = entry->pointer; /* pointer indirection */
 
     if (entry)
         c = entry->tp;
     else
-        c = ' ';
+        c = NUPA_SPACE;
 
-    if ((c == 'R') || (c == 'S') || (c == '?')) {
+    if ((c == NUPA_REAL) || (c == NUPA_STRING) || (c == NUPA_UNKNOWN)) {
 
         entry->vl = z;
         entry->tp = tpe;
         entry->ivl = w;
         entry->sbbase = base;
         /* if ((c != '?') && (i <= dico->stack[dico->tos])) { */
-        if (c == '?')
+        if (c == NUPA_UNKNOWN)
             entry->level = dico->stack_depth; /* promote! */
 
         /* warn about re-write to a global scope! */
@@ -533,7 +533,7 @@ nupa_define(dico_t *dico,
 
 
 bool
-defsubckt(dico_t *dico, struct card *card, char categ)
+defsubckt(dico_t *dico, struct card *card, nupa_type categ)
 /* called on 1st pass of spice source code,
    to enter subcircuit (categ=U) and model (categ=O) names
 */
@@ -601,7 +601,7 @@ findsubckt(dico_t *dico, char *s, SPICE_DSTRINGPTR subname)
     pscopy_up(&ustr, s, k + 1, j - k);
     entry = entrynb(dico, spice_dstring_value(&ustr));
 
-    if (entry && (entry->tp == 'U')) {
+    if (entry && (entry->tp == NUPA_SUBCKT)) {
         line = entry->ivl;
         scopyd(subname, &ustr);
     } else {
@@ -1114,7 +1114,7 @@ evaluate(dico_t *dico, SPICE_DSTRINGPTR qstr_p, char *t, unsigned char mode)
     /* transform t to result q. mode 0: expression, mode 1: simple variable */
     double u = 0.0;
     int j, lq;
-    char dt;
+    nupa_type dt;
     entry_t *entry;
     bool numeric, done, nolookup;
     bool err;
@@ -1129,7 +1129,7 @@ evaluate(dico_t *dico, SPICE_DSTRINGPTR qstr_p, char *t, unsigned char mode)
         entry = entrynb(dico, t);
         nolookup = !entry;
 
-        while (entry && (entry->tp == 'P'))
+        while (entry && (entry->tp == NUPA_POINTER))
             entry = entry->pointer; /* follow pointer chain */
 
         if (!entry)
@@ -1140,10 +1140,10 @@ evaluate(dico_t *dico, SPICE_DSTRINGPTR qstr_p, char *t, unsigned char mode)
         dt = entry->tp;
 
         /* data type: Real or String */
-        if (dt == 'R') {
+        if (dt == NUPA_REAL) {
             u = entry->vl;
             numeric = 1;
-        } else if (dt == 'S') {
+        } else if (dt == NUPA_STRING) {
             /* suppose source text "..." at */
             j = entry->ivl;
             lq = 0;
@@ -1383,7 +1383,7 @@ getword(char *s, SPICE_DSTRINGPTR tstr_p, int after, int *pi)
 }
 
 
-static char
+static nupa_type
 getexpress(char *s, SPICE_DSTRINGPTR tstr_p, int *pi)
 /* returns expression-like string until next separator
    Input  i=position before expr, output  i=just after expr, on separator.
@@ -1392,7 +1392,8 @@ getexpress(char *s, SPICE_DSTRINGPTR tstr_p, int *pi)
 {
     int i = *pi;
     int ia, ls, level;
-    char c, d, tpe;
+    char c, d;
+    nupa_type tpe;
 
     ls = length(s);
     ia = i + 1;
@@ -1408,7 +1409,7 @@ getexpress(char *s, SPICE_DSTRINGPTR tstr_p, int *pi)
         while ((i < ls) && (s[i - 1] != '"'))
             i++;
 
-        tpe = 'S';
+        tpe = NUPA_STRING;
 
         do
             i++;
@@ -1452,7 +1453,7 @@ getexpress(char *s, SPICE_DSTRINGPTR tstr_p, int *pi)
 
         } while (!(cpos (c, ",;)}") >= 0)); /* legal separators */
 
-        tpe = 'R';
+        tpe = NUPA_REAL;
     }
 
     pscopy(tstr_p, s, ia-1, i - ia);
@@ -1460,7 +1461,7 @@ getexpress(char *s, SPICE_DSTRINGPTR tstr_p, int *pi)
     if (s[i - 1] == '}')
         i++;
 
-    if (tpe == 'S')
+    if (tpe == NUPA_STRING)
         i++;                    /* beyond quote */
 
     *pi = i;
@@ -1480,7 +1481,7 @@ nupa_assignment(dico_t *dico, char *s, char mode)
     /* s has the format: ident = expression; ident= expression ...  */
     int i, ls;
     bool error, err;
-    char dtype;
+    nupa_type dtype;
     int wval = 0;
     double rval = 0.0;
     char *t_p;                  /* dstring contents value */
@@ -1520,14 +1521,14 @@ nupa_assignment(dico_t *dico, char *s, char mode)
 
             dtype = getexpress(s, &ustr, &i);
 
-            if (dtype == 'R') {
+            if (dtype == NUPA_REAL) {
                 const char *tmp = spice_dstring_value(&ustr);
                 rval = formula(dico, tmp, tmp + strlen(tmp), &error);
                 if (error)
                     message(dico,
                             " Formula() error.\n"
                             "      %s\n", s);
-            } else if (dtype == 'S') {
+            } else if (dtype == NUPA_STRING) {
                 wval = i;
             }