diff --git a/scp.c b/scp.c
index 14c2c927..afa506c4 100644
--- a/scp.c
+++ b/scp.c
@@ -464,6 +464,7 @@ t_stat set_dev_radix (DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
 t_stat set_dev_enbdis (DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
 t_stat set_dev_debug (DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
 t_stat set_unit_enbdis (DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
+t_stat set_unit_append (DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
 t_stat ssh_break (FILE *st, const char *cptr, int32 flg);
 t_stat show_cmd_fi (FILE *ofile, int32 flag, CONST char *cptr);
 t_stat show_config (FILE *st, DEVICE *dptr, UNIT *uptr, int32 flag, CONST char *cptr);
@@ -2506,6 +2507,8 @@ static C1TAB set_dev_tab[] = {
     { "DISABLED",   &set_dev_enbdis,    0 },
     { "DEBUG",      &set_dev_debug,     1 },
     { "NODEBUG",    &set_dev_debug,     0 },
+    { "APPEND",     &set_unit_append,   0 },
+    { "EOF",        &set_unit_append,   0 },
     { NULL,         NULL,               0 }
     };
 
@@ -2514,6 +2517,8 @@ static C1TAB set_unit_tab[] = {
     { "DISABLED",   &set_unit_enbdis,   0 },
     { "DEBUG",      &set_dev_debug,     2+1 },
     { "NODEBUG",    &set_dev_debug,     2+0 },
+    { "APPEND",     &set_unit_append,   0 },
+    { "EOF",        &set_unit_append,   0 },
     { NULL,         NULL,               0 }
     };
 
@@ -3231,6 +3236,16 @@ if ((dptr->modifiers) && (dptr->units) && (enabled_units != 1)) {
             }
         }
     }
+if (enabled_units) {
+    for (unit=0; unit < dptr->numunits; unit++)
+        if ((!(dptr->units[unit].flags & UNIT_DIS)) &&
+            (dptr->units[unit].flags & UNIT_SEQ) && 
+            (!(dptr->units[unit].flags & UNIT_MUSTBUF))) {
+            sprintf (buf, "set %s%s APPEND", sim_uname (&dptr->units[unit]), (enabled_units > 1) ? "n" : "");
+            fprintf (st,  "%-30s\tSets %s position to EOF\n", buf, sim_uname (&dptr->units[unit]), (enabled_units > 1) ? "n" : "");
+            break;
+            }
+    }
 if (deb_desc_available) {
     fprintf (st, "\n*%s device DEBUG settings:\n", sim_dname (dptr));
     for (dep = dptr->debflags; dep->name != NULL; dep++)
@@ -5560,7 +5575,7 @@ else {
     for (i = 0; i < dptr->numunits; i++) {              /* check units */
         up = (dptr->units) + i;                         /* att or active? */
         if ((up->flags & UNIT_ATT) || sim_is_active (up))
-            return SCPE_NOFNC;                          /* can't do it */
+            return sim_messagef (SCPE_NOFNC, "%s has attached or busy units\n", sim_dname (dptr));                          /* can't do it */
         }
     dptr->flags = dptr->flags | DEV_DIS;                /* disable */
     }
@@ -5582,7 +5597,7 @@ if (flag)                                               /* enb? enable */
 else {
     if ((uptr->flags & UNIT_ATT) ||                     /* dsb */
         sim_is_active (uptr))                           /* more tests */
-        return SCPE_NOFNC;
+        return sim_messagef (SCPE_NOFNC, "%s is attached or busy\n", sim_uname (uptr));
     uptr->flags = uptr->flags | UNIT_DIS;               /* disable */
     }
 return SCPE_OK;
@@ -5639,6 +5654,25 @@ while (*cptr) {
 return r;
 }
 
+/* Set sequential unit position to EOF */
+
+t_stat set_unit_append (DEVICE *dptr, UNIT *uptr, int32 flags, CONST char *cptr)
+{
+if (!(uptr->flags & UNIT_SEQ))
+    return sim_messagef (SCPE_NOFNC, "%s is not a sequential device.\n", sim_uname (uptr));
+if (uptr->flags & UNIT_BUF)
+    return sim_messagef (SCPE_NOFNC, "Can't append to a buffered device %s.\n", sim_uname (uptr));
+if (!(uptr->flags & UNIT_ATT))
+    return SCPE_UNATT;
+
+if (0 == sim_fseek (uptr->fileref, 0, SEEK_END)) {
+    uptr->pos = (t_addr)sim_ftell (uptr->fileref);      /* Position at end of file */
+    return SCPE_OK;
+    }
+
+return sim_messagef (SCPE_IERR, "%s Can't seek to end of file: %s - %s\n", sim_uname (uptr), uptr->filename, strerror (errno));
+}
+
 /* Show command */
 
 t_stat show_cmd (int32 flag, CONST char *cptr)
@@ -9266,7 +9300,10 @@ if (flag & EX_I) {
         return dfltinc;
     }
 if (uptr->flags & UNIT_RO)                              /* read only? */
-    return SCPE_RO;
+    return sim_messagef (SCPE_RO, "%s is read only.\n"
+                                  "%sse a writable device to change %s\n", 
+                                  sim_uname (uptr), (uptr->flags & UNIT_ROABLE) ? "Attach Read/Write or u" : "U",
+                                  uptr->filename ? uptr->filename : "it");
 mask = width_mask[dptr->dwidth];
 
 GET_RADIX (rdx, dptr->dradix);