diff --git a/jsrc/dstop.c b/jsrc/dstop.c
index 1cc1d5b8b..2e2e09708 100644
--- a/jsrc/dstop.c
+++ b/jsrc/dstop.c
@@ -13,18 +13,20 @@
 /*              monad line numbers and dyad line numbers (* means all). */
 /* ~abc*yz m:d  don't stop                                              */
 
+// p points to stop numbers, nw is character form of line number (must be canonical), md=1 for monad, 2 for dyad
+// result is 1 if there is a stop on this line 
 static B stopsub(C*p,C*nw,I md){C*q,*s;I n;
- s=strchr(p,';'); if(!s)s=p+strlen(p);
- q=strchr(p,':'); if(!q||q>s)q=s;
- if(2==md){p=q; q=s; if(':'==*p)++p;}
- s=strchr(p,'*'); if(s&&q>s)R 1;
- n=strlen(nw);
- while(q>p){
-  NOUNROLL while(' '==*p)++p;
-  if(!strncmp(p,nw,n)&&(q==p+n||' '==p[n]))R 1;
-  NOUNROLL while(q>p&&' '!=*p)++p;
+ s=strchr(p,';'); if(!s)s=p+strlen(p);  // s-> end+1-of-line#s (first ; or ending NUL)
+ q=strchr(p,':'); if(!q||q>s)q=s;  // q-> end+1-of-monad-line#s (first : or s)
+ if(2==md){p=q; q=s; if(':'==*p)++p;}  // adjust for dyad.  Now p=start of line#s, q=end+1 of line#s
+ s=strchr(p,'*'); if(s&&q>s)R 1;   // if '*' in the line#s, return true
+ n=strlen(nw);    // n=length of line# we are looking for (in canonical form)
+ while(q>p){    // until all #s checked...
+  NOUNROLL while(' '==*p)++p;  // skip leading blanks
+  if(!strncmp(p,nw,n)&&(q==p+n||' '==p[n]))R 1;   // match strings for the length of the name & verify stopnum is at the end; if so, success
+  NOUNROLL while(q>p&&' '!=*p)++p;   // skip unmatched part of stopnum
  }
- R 0;
+ R 0;   // no stopnum matched, return failure
 }
 
 // i is the line we are about to execute, c is the call-stack entry for the current function
@@ -46,13 +48,13 @@ B jtdbstop(J jt,DC d,I i){A a;B b,c=0,e;C nw[11],*s,*t,*u,*v;I md,n,p,q;
  if((d->dca&&JT(jt,dbstops))){  // if the name is given and there are stops...
   s=CAV(str0(JT(jt,dbstops))); sprintf(nw,FMTI,i);  // s->stop strings, nw=character form of line#
   a=d->dca; n=NAV(a)->m; t=NAV(a)->s; md=d->dcx&&d->dcy?2:1;   // t->name we are looking for, n=its length, md=valence of call
-  NOUNROLL while(s){
-   NOUNROLL while(' '==*s)++s; if(b='~'==*s)++s; while(' '==*s)++s;
-   u=strchr(s,'*'); v=strchr(s,' '); if(!v)break; 
-   if(!u||u>v)e=!strncmp(s,t,MAX(n,v-s));
-   else{p=u-s; q=v-u-1; e=p<=n&&!strncmp(s,t,p)&&q<=n&&!strncmp(1+u,t+n-q,q);}
-   if(e){s=1+v; if(stopsub(s,nw,md)){if(b){c=0; break;} c=1;}}
-   s=strchr(s,';'); if(s)++s;
+  NOUNROLL while(s){  // until we have looked at all stops...
+   NOUNROLL while(' '==*s)++s; if(b='~'==*s)++s; while(' '==*s)++s;  // skip over spaces and ~.  Set b = '~' found
+   u=strchr(s,'*'); v=strchr(s,' '); if(!v)break;   // u=address of first '*' if any; v=first space if any; if no space, it's name with no stops, quit
+   if(!u||u>v)e=!strncmp(s,t,MAX(n,v-s));   // if there is no * before the first space, set e to 'names match in full'
+   else{p=u-s; q=v-u-1; e=p<=n&&!strncmp(s,t,p)&&q<=n&&!strncmp(1+u,t+n-q,q);}  // p=length of stopname before *, v=length of stopname after *, e to 'names match' if both parts matched
+   if(e){s=1+v; if(stopsub(s,nw,md)){if(b){c=0; break;} c=1;}}  // if matched, point to line numbers and see if there is a stop.  If there is, if it's not ~ set c and continue (there might be a later ~); if ~, exit 'no stop'
+   s=strchr(s,';'); if(s)++s;  // advance to ; if any (s=0 if no ;) and then beyond
   }
   if(c){d->dcstop=i;  NOUNROLL while(d){if(d->dctype==DCCALL)d->dcss=0; d=d->dclnk;}}  // if stop found, turn off single-step everywhere
   else  d->dcstop=-2;