diff --git a/src/frontend/dvec.c b/src/frontend/dvec.c
index 6da1d44a3..f837f17e3 100644
--- a/src/frontend/dvec.c
+++ b/src/frontend/dvec.c
@@ -7,35 +7,51 @@ dvec_alloc(char *name, int type, short flags, int length, void *storage)
 {
     struct dvec *rv = TMALLOC(struct dvec, 1);
 
-    if (!rv)
+    /* If the allocation failed, return NULL as a failure flag.
+     * As of 2019-03, TMALLOC will not return on failure, so this check is
+     * redundant, but it may be useful if it is decided to allow the
+     * allocation functions to return NULL on failure and handle recovery
+     * by the calling functions */
+    if (!rv) {
         return NULL;
+    }
 
+    /* Set all fields to 0 */
     ZERO(rv, struct dvec);
 
+    /* Set information on the vector from parameters. Note that storage for
+     * the name string belongs to the dvec when this function returns. */
     rv->v_name = name;
     rv->v_type = type;
     rv->v_flags = flags;
     rv->v_length = length;
     rv->v_alloc_length = length;
 
-    if (!length) {
+    if (length == 0) { /* Redundant due to ZERO() call above */
         rv->v_realdata = NULL;
         rv->v_compdata = NULL;
-    } else if (flags & VF_REAL) {
+    }
+    else if (flags & VF_REAL) {
+        /* Vector consists of real data. Use the supplied storage if given
+         * or allocate if not */
         rv->v_realdata = storage
             ? (double *) storage
             : TMALLOC(double, length);
         rv->v_compdata = NULL;
-    } else if (flags & VF_COMPLEX) {
+    }
+    else if (flags & VF_COMPLEX) {
+        /* Vector holds complex data. Perform actions as for real data */
         rv->v_realdata = NULL;
         rv->v_compdata = storage
             ? (ngcomplex_t *) storage
             : TMALLOC(ngcomplex_t, length);
     }
 
+    /* Set remaining fields to none/unknown. Again not required due to
+     * the ZERO() call */
     rv->v_plot = NULL;
     rv->v_scale = NULL;
-    rv->v_numdims = 0;
+    rv->v_numdims = 0; /* Really "unknown" */
 
     return rv;
 }
diff --git a/src/frontend/parser/complete.c b/src/frontend/parser/complete.c
index 59b1252ce..794ae3b3a 100644
--- a/src/frontend/parser/complete.c
+++ b/src/frontend/parser/complete.c
@@ -73,8 +73,8 @@ static void printem(wordlist *wl);
 #endif
 
 static wordlist *cctowl(struct ccom *cc, bool sib);
-static struct ccom *clookup(register char *word, struct ccom **dd, bool pref,
-                            bool create);
+static struct ccom *clookup(register const char *word, struct ccom **dd, bool pref,
+        bool create);
 /* MW. I need top node in cdelete */
 static void cdelete(struct ccom *node, struct ccom **top);
 
@@ -515,7 +515,7 @@ cp_destroy_keywords(void)
 /* Remove a keyword from the database. */
 
 void
-cp_remkword(int kw_class, char *word)
+cp_remkword(int kw_class, const char *word)
 {
     struct ccom *cc;
 
@@ -583,7 +583,7 @@ throwaway(struct ccom *dbase)
  */
 
 static struct ccom *
-clookup(register char *word, struct ccom **dd, bool pref, bool create)
+clookup(register const char *word, struct ccom **dd, bool pref, bool create)
 {
     register struct ccom *place = *dd, *tmpc;
     int ind = 0, i;
diff --git a/src/frontend/vectors.c b/src/frontend/vectors.c
index f58d61141..dc1001f1b 100644
--- a/src/frontend/vectors.c
+++ b/src/frontend/vectors.c
@@ -339,7 +339,7 @@ plot_add(struct plot *pl)
 /* Remove a vector from the database, if it is there. */
 
 void
-vec_remove(char *name)
+vec_remove(const char *name)
 {
     struct dvec *ov;
 
@@ -769,12 +769,20 @@ vec_new(struct dvec *d)
         plot_cur->pl_scale = d;
     if (!d->v_plot)
         d->v_plot = plot_cur;
+
+    /* This code appears to be a patch for incorrectly specified vectors */
     if (d->v_numdims < 1) {
         d->v_numdims = 1;
         d->v_dims[0] = d->v_length;
     }
-    d->v_next = d->v_plot->pl_dvecs;
-    d->v_plot->pl_dvecs = d;
+
+    {
+        /* Make this vector the first plot vector and link the old first plot
+         * vector via its next pointer */
+        struct plot *v_plot = d->v_plot;
+        d->v_next = v_plot->pl_dvecs;
+        v_plot->pl_dvecs = d;
+    }
 }
 
 
diff --git a/src/include/ngspice/cpextern.h b/src/include/ngspice/cpextern.h
index 314d6ae5f..fd079bb84 100644
--- a/src/include/ngspice/cpextern.h
+++ b/src/include/ngspice/cpextern.h
@@ -43,7 +43,7 @@ extern void cp_ccom(wordlist *wlist, char *buf, bool esc);
 extern void cp_ccon(bool on);
 extern void cp_ccrestart(bool kwords);
 extern void cp_remcomm(char *word);
-extern void cp_remkword(int kw_class, char *word);
+extern void cp_remkword(int kw_class, const char *word);
 extern void cp_destroy_keywords(void);
 
 extern wordlist *cp_cctowl(struct ccom *stuff);
diff --git a/src/include/ngspice/fteext.h b/src/include/ngspice/fteext.h
index 699090c6b..d8b5aafd6 100644
--- a/src/include/ngspice/fteext.h
+++ b/src/include/ngspice/fteext.h
@@ -357,7 +357,7 @@ extern void vec_gc(void);
 extern void ft_loadfile(char *file);
 extern void vec_new(struct dvec *d);
 extern void plot_docoms(wordlist *wl);
-extern void vec_remove(char *name);
+extern void vec_remove(const char *name);
 extern void plot_setcur(char *name);
 extern struct plot *get_plot(char* name);
 extern void plot_new(struct plot *pl);
diff --git a/src/misc/string.c b/src/misc/string.c
index 5279c4a43..ed89a3582 100644
--- a/src/misc/string.c
+++ b/src/misc/string.c
@@ -75,22 +75,34 @@ tvprintf(const char *fmt, va_list args)
 
         if (nchars == -1) {     // compatibility to old implementations
             size *= 2;
-        } else if (size < nchars + 1) {
-            size = nchars + 1;
-        } else {
+        }
+        else if (nchars >= size) {
+            /* Output was truncated. Returned value is the number of chars
+             * that would have been written if the buffer were large enough
+             * excluding the terminiating null. */
+            size = nchars + 1; /* min required allocation size */
+        }
+        else { /* String formatted OK */
             break;
         }
 
+        /* Allocate a larger buffer */
         if (p == buf)
             p = TMALLOC(char, size);
         else
             p = TREALLOC(char, p, size);
     }
 
+    /* Return the formatted string, making a copy on the heap if the
+     * stack's buffer (buf) contains the string */
     return (p == buf) ? copy(p) : p;
-}
+} /* end of function tvprintf */
 
 
+
+/* This function returns an allocation containing the string formatted
+ * according to fmt and the variadic argument list provided. It is a wrapper
+ * around tvprintf() which processes the argumens as a va_list. */
 char *
 tprintf(const char *fmt, ...)
 {
@@ -102,7 +114,7 @@ tprintf(const char *fmt, ...)
     va_end(ap);
 
     return rv;
-}
+} /* end of function tprintf */
 
 
 /* Determine whether sub is a substring of str. */