diff --git a/doc/sigma_doc.doc b/doc/sigma_doc.doc
new file mode 100644
index 00000000..40f24e77
Binary files /dev/null and b/doc/sigma_doc.doc differ
diff --git a/sigma/sigma_cis.c b/sigma/sigma_cis.c
index 969cee88..10afdd43 100644
--- a/sigma/sigma_cis.c
+++ b/sigma/sigma_cis.c
@@ -1,6 +1,6 @@
 /* sigma_cis.c: Sigma decimal instructions
 
-   Copyright (c) 2007-2008, Robert M Supnik
+   Copyright (c) 2007-2018, Robert M Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -26,6 +26,8 @@
    Questions:
 
    1. On the Sigma 9, in ASCII mode, is an ASCII blank used in EBS?
+
+   02-Jun-2018  RMS     Fixed unsigned < 0 in decimal compare (Mark Pizzolato)
 */
 
 #include "sigma_defs.h"
@@ -100,7 +102,7 @@ uint32 cis_dec (uint32 op, uint32 lnt, uint32 bva)
 {
 dstr_t src1, src2, src2x, dst;
 uint32 i, t, kint, ldivr, ldivd, ad, c, d, end;
-int32 sc;
+int32 sc, scmp;
 uint32 tr;
 
 if (lnt == 0)                                           /* adjust length */
@@ -163,10 +165,10 @@ switch (op) {                                           /* case on opcode */
         if (src1.sign ^ src2.sign)                      /* signs differ? */
             CC = src1.sign? CC4: CC3;                   /* set < or > */
         else {                                          /* same signs */
-            t = CmpDstr (&src1, &src2);                 /* compare strings */
-            if (t < 0)
+            scmp = CmpDstr (&src1, &src2);              /* compare strings */
+            if (scmp < 0)
                 CC = (src1.sign? CC3: CC4);
-            else if (t > 0)
+            else if (scmp > 0)
                 CC = (src1.sign? CC4: CC3);
             else CC = 0;
             }
@@ -841,7 +843,7 @@ uint32 NibbleRshift (dstr_t *dsrc, uint32 sc, uint32 cin)
 int32 i;
 uint32 s, nc;
 
-if (s = sc * 4) {
+if ((s = sc * 4)) {
     for (i = DSTRLNT - 1; (int32) i >= 0; i--) {
         nc = (dsrc->val[i] << (32 - s)) & WMASK;
         dsrc->val[i] = ((dsrc->val[i] >> s) |
@@ -865,7 +867,7 @@ uint32 NibbleLshift (dstr_t *dsrc, uint32 sc, uint32 cin)
 {
 uint32 i, s, nc;
 
-if (s = sc * 4) {
+if ((s = sc * 4)) {
     for (i = 0; i < DSTRLNT; i++) {
         nc = dsrc->val[i] >> (32 - s);
         dsrc->val[i] = ((dsrc->val[i] << s) |
diff --git a/sigma/sigma_coc.c b/sigma/sigma_coc.c
index 5fdaad53..97f4bf4b 100644
--- a/sigma/sigma_coc.c
+++ b/sigma/sigma_coc.c
@@ -97,9 +97,9 @@ t_stat muxc_svc (UNIT *uptr);
 t_stat muxo_svc (UNIT *uptr);
 t_stat muxi_rtc_svc (UNIT *uptr);
 t_stat mux_reset (DEVICE *dptr);
-t_stat mux_attach (UNIT *uptr, char *cptr);
+t_stat mux_attach (UNIT *uptr, CONST char *cptr);
 t_stat mux_detach (UNIT *uptr);
-t_stat mux_vlines (UNIT *uptr, int32 val, char *cptr, void *desc);
+t_stat mux_vlines (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
 void mux_reset_ln (int32 ln);
 void mux_scan_next (t_bool clr);
 t_stat muxi_put_char (uint32 c, uint32 ln);
@@ -417,7 +417,7 @@ if ((newln >= 0) && (mux_sta[newln] & MUXL_REP)) {      /* rcv enb pending? */
 tmxr_poll_rx (&mux_desc);                               /* poll for input */
 for (ln = 0; ln < MUX_NUMLIN; ln++) {                   /* loop thru lines */
     if (mux_ldsc[ln].conn) {                            /* connected? */
-        if (c = tmxr_getc_ln (&mux_ldsc[ln])) {         /* get char */
+        if ((c = tmxr_getc_ln (&mux_ldsc[ln]))) {       /* get char */
             if (c & SCPE_BREAK)                         /* break? */
                 mux_sta[ln] |= MUXL_RBP;                /* set rcv brk */
             else {                                      /* normal char */
@@ -544,7 +544,7 @@ return SCPE_OK;
 
 /* Attach master unit */
 
-t_stat mux_attach (UNIT *uptr, char *cptr)
+t_stat mux_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat r;
 
@@ -572,7 +572,7 @@ return r;
 
 /* Change number of lines */
 
-t_stat mux_vlines (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat mux_vlines (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 newln, i, t;
 t_stat r;
diff --git a/sigma/sigma_cpu.c b/sigma/sigma_cpu.c
index 2b14802b..87903d96 100644
--- a/sigma/sigma_cpu.c
+++ b/sigma/sigma_cpu.c
@@ -190,17 +190,17 @@ t_stat cpu_svc (UNIT *uptr);
 t_stat cpu_ex (t_value *vptr, t_addr addr, UNIT *uptr, int32 sw);
 t_stat cpu_dep (t_value val, t_addr addr, UNIT *uptr, int32 sw);
 t_stat cpu_reset (DEVICE *dptr);
-t_stat cpu_set_size (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_set_type (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_set_opt (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_clr_opt (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_set_rblks (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_show_rblks (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat cpu_set_hist (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat cpu_set_alarm (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat cpu_show_alarm (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat cpu_show_addr (FILE *st, UNIT *uptr, int32 val, void *desc);
+t_stat cpu_set_size (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_set_type (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_set_opt (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_clr_opt (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_set_rblks (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_show_rblks (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat cpu_set_hist (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat cpu_set_alarm (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat cpu_show_alarm (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat cpu_show_addr (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 void set_rf_display (uint32 *rfbase);
 void inst_hist (uint32 ir, uint32 pc, uint32 typ);
 uint32 cpu_one_inst (uint32 real_pc, uint32 IR);
@@ -252,8 +252,8 @@ extern uint32 int_reset (DEVICE *dev);
 extern void io_set_eimax (uint32 lnt);
 extern void io_sclr_req (uint32 inum, uint32 val);
 extern void io_sclr_arm (uint32 inum, uint32 val);
-extern t_stat io_set_nchan (UNIT *uptr, int32 val, char *cptr, void *desc);
-extern t_stat io_show_nchan (FILE *st, UNIT *uptr, int32 val, void *desc);
+extern t_stat io_set_nchan (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+extern t_stat io_show_nchan (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 
 /* CPU data structures
 
@@ -436,7 +436,7 @@ while (reason == 0) {                                   /* loop until stop */
         }
 
     if (sim_interval <= 0) {                            /* event queue? */
-        if (reason = sim_process_event ())              /* process */
+        if ((reason = sim_process_event ()))            /* process */
             break;
         int_hireq = io_eval_int ();                     /* re-evaluate intr */
         }
@@ -2575,7 +2575,7 @@ return SCPE_OK;
 
 /* Set CPU type */
 
-t_stat cpu_set_type (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_type (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 model = CPUF_GETMOD (val);
 
@@ -2593,7 +2593,7 @@ return SCPE_OK;
 
 /* Set memory size */
 
-t_stat cpu_set_size (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_size (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 mc = 0;
 uint32 i;
@@ -2614,7 +2614,7 @@ return SCPE_OK;
 
 /* Set and clear options */
 
-t_stat cpu_set_opt (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_opt (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 if ((val & (cpu_tab[cpu_model].std | cpu_tab[cpu_model].opt)) == 0)
     return SCPE_NOFNC;
@@ -2622,7 +2622,7 @@ cpu_unit.flags |= val;
 return SCPE_OK;
 }
 
-t_stat cpu_clr_opt (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_clr_opt (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 if (val & cpu_tab[cpu_model].std)
     return SCPE_NOFNC;
@@ -2632,7 +2632,7 @@ return SCPE_OK;
 
 /* Set/show register blocks */
 
-t_stat cpu_set_rblks (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_rblks (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 invmask, lnt, i, j;
 t_stat r;
@@ -2656,7 +2656,7 @@ for (i = rf_bmax; i < RF_NBLK; i++) {                   /* zero unused */
 return SCPE_OK;
 }
 
-t_stat cpu_show_rblks (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat cpu_show_rblks (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fprintf (st, "register blocks=%d", rf_bmax);
 return SCPE_OK;
@@ -2678,13 +2678,13 @@ return;
 
 /* Front panael alarm */
 
-t_stat cpu_set_alarm (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_alarm (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 cons_alarm_enb = val;
 return SCPE_OK;
 }
 
-t_stat cpu_show_alarm (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat cpu_show_alarm (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fputs (cons_alarm_enb? "alarm enabled\n": "alarm disabled\n", st);
 return SCPE_OK;
@@ -2701,7 +2701,7 @@ return SCPE_OK;
 
 /* Virtual address translation */
 
-t_stat cpu_show_addr (FILE *of, UNIT *uptr, int32 val, void *desc)
+t_stat cpu_show_addr (FILE *of, UNIT *uptr, int32 val, CONST void *desc)
 {
 t_stat r;
 char *cptr = (char *) desc;
@@ -2757,7 +2757,7 @@ return;
 
 /* Set history */
 
-t_stat cpu_set_hist (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat cpu_set_hist (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 i, lnt;
 t_stat r;
@@ -2820,7 +2820,7 @@ return;
 
 /* Show history */
 
-t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat cpu_show_hist (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 int32 k, di, lnt;
 t_stat r;
diff --git a/sigma/sigma_defs.h b/sigma/sigma_defs.h
index 5cf5925f..e2f85d3b 100644
--- a/sigma/sigma_defs.h
+++ b/sigma/sigma_defs.h
@@ -319,7 +319,7 @@ typedef struct {
 #define MMC_M_CNT       0xFF
 #define MMC_CNT         (MMC_M_CNT << MMC_V_CNT)
 #define MMC_V_CS        9                               /* start of page */
-/*                                                      /* map 1: 2b locks, per model */
+                                                        /* map 1: 2b locks, per model */
 #define MMC_M_CS2       0xFC                            /* map 2: access controls */
 #define MMC_M_CS3       0x7FE                           /* map 3: 4b locks */
 #define MMC_M_CS4       0xFF                            /* map 4: 8b relocation */
diff --git a/sigma/sigma_dp.c b/sigma/sigma_dp.c
index 1f56d321..324dbaf0 100644
--- a/sigma/sigma_dp.c
+++ b/sigma/sigma_dp.c
@@ -158,14 +158,14 @@
    type         #sectors/       #surfaces/      #cylinders/
                  surface         cylinder        drive
 
-   7242         6               20              203		    =24MB
-   7261         11              20              203		    =45MB
-   7271         6               20              406		    =48MB
+   7242         6               20              203         =24MB
+   7261         11              20              203         =45MB
+   7271         6               20              406         =48MB
    3288         17              5               822         =67MB
    7276         11              19              411         =86MB
    7266         11              20              411         =90MB
-   3282         11              19              815		    =170MB
-   3283         17              19              815		    =263MB
+   3282         11              19              815         =170MB
+   3283         17              19              815         =263MB
 
    On the T3281, each drive can be a different type.  The size field
    in each unit selects the drive capacity for each drive and thus
@@ -290,11 +290,11 @@ t_bool dp_end_sec (UNIT *uptr, uint32 lnt, uint32 exp, uint32 st);
 int32 dp_clr_int (uint32 cidx);
 void dp_set_ski (uint32 cidx, uint32 un);
 void dp_clr_ski (uint32 cidx, uint32 un);
-t_stat dp_attach (UNIT *uptr, char *cptr);
-t_stat dp_set_size (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat dp_set_auto (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat dp_set_ctl (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat dp_show_ctl (FILE *st, UNIT *uptr, int32 val, void *desc);
+t_stat dp_attach (UNIT *uptr, CONST char *cptr);
+t_stat dp_set_size (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat dp_set_auto (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat dp_set_ctl (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat dp_show_ctl (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 
 static DP_TYPE dp_tab[] = {
     { DP_ENT (7242, 7240) },
@@ -776,7 +776,7 @@ switch (uptr->UCMD) {
             else wd = 0;
             dp_buf[i] = wd;                             /* store in buffer */
             }
-        if (r = dp_write (uptr, da))                    /* write buf, err? */
+        if ((r = dp_write (uptr, da)))                  /* write buf, err? */
             return r;
         if (dp_end_sec (uptr, DP_WDSC, DP_WDSC, st))    /* transfer done? */
             return SCPE_OK;                             /* err or cont */
@@ -818,7 +818,7 @@ switch (uptr->UCMD) {
             chan_uen (dva);                             /* uend */
             return SCPE_OK;
             }
-        if (r = dp_read (uptr, da))                     /* read buf, error? */
+        if ((r = dp_read (uptr, da)))                   /* read buf, error? */
             return r;
         for (i = 0, st = 0; (i < (DP_WDSC * 4)) && (st != CHS_ZBC); i++) {
             st = chan_RdMemB (dva, &wd);                /* read byte */
@@ -843,7 +843,7 @@ switch (uptr->UCMD) {
             chan_uen (dva);                             /* uend */
                 return SCPE_OK;
             }
-        if (r = dp_read (uptr, da))                     /* read buf, error? */
+        if ((r = dp_read (uptr, da)))                   /* read buf, error? */
             return r;
         for (i = 0, st = 0; (i < DP_WDSC) && (st != CHS_ZBC); i++) {
             st = chan_WrMemW (dva, dp_buf[i]);          /* store in mem */
@@ -1225,7 +1225,7 @@ return SCPE_OK;
 
 /* Device attach */
 
-t_stat dp_attach (UNIT *uptr, char *cptr)
+t_stat dp_attach (UNIT *uptr, CONST char *cptr)
 {
 uint32 i, p;
 t_stat r;
@@ -1252,7 +1252,7 @@ return SCPE_OK;
 
 /* Set drive type command validation routine */
 
-t_stat dp_set_size (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat dp_set_size (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 dtype = GET_DTYPE (val);
 uint32 cidx = uptr->UCTX;
@@ -1269,7 +1269,7 @@ return SCPE_OK;
 
 /* Set unit autosize validation routine */
 
-t_stat dp_set_auto (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat dp_set_auto (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 cidx = uptr->UCTX;
 
@@ -1284,7 +1284,7 @@ return SCPE_OK;
 
 /* Set controller type command validation routine */
 
-t_stat dp_set_ctl (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat dp_set_ctl (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 i, new_dtyp, cidx = uptr->UCTX;
 DP_CTX *ctx = &dp_ctx[cidx];
@@ -1320,7 +1320,7 @@ for (i = 0; i < DP_NUMDR_16B; i++) {
 return SCPE_OK;
 }
 
-t_stat dp_show_ctl (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat dp_show_ctl (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 uint32 cidx = uptr->UCTX;
 
diff --git a/sigma/sigma_io.c b/sigma/sigma_io.c
index d7f96d52..4d85a299 100644
--- a/sigma/sigma_io.c
+++ b/sigma/sigma_io.c
@@ -101,8 +101,8 @@ t_bool io_init_inst (uint32 ad, uint32 rn, uint32 ch, uint32 dev, uint32 r0);
 uint32 io_set_status (uint32 rn, uint32 ch, uint32 dev, uint32 dvst, t_bool tdv);
 uint32 io_rwd_m0 (uint32 op, uint32 rn, uint32 ad);
 uint32 io_rwd_m1 (uint32 op, uint32 rn, uint32 ad);
-t_stat io_set_eiblks (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat io_show_eiblks (FILE *st, UNIT *uptr, int32 val, void *desc);
+t_stat io_set_eiblks (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat io_show_eiblks (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 t_stat int_reset (DEVICE *dptr);
 t_stat chan_reset (DEVICE *dptr);
 uint32 chan_new_cmd (uint32 ch, uint32 dev, uint32 clc);
@@ -1043,7 +1043,7 @@ if (op == OP_RD) {                                      /* read direct? */
         }
     else if (QCPU_S89 && (fnc == 0x045)) {              /* S89 only */
         if (rn)
-            R[rn] = s9_marg & 0x00C00000 |              /* <8,9> = margins */
+            R[rn] = (s9_marg & 0x00C00000) |            /* <8,9> = margins */
                 (QCPU_S9? 0x00100000: 0x00200000);      /* S8 sets 10, S9 11 */            
         }
     else if (QCPU_S89 && (fnc == 0x049)) {              /* S89 only */
@@ -1307,7 +1307,7 @@ return SCPE_OK;
 
 /* Set/show external interrupt blocks */
 
-t_stat io_set_eiblks (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat io_set_eiblks (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 lnt;
 t_stat r;
@@ -1322,7 +1322,7 @@ io_set_eimax (lnt);
 return SCPE_OK;
 }
 
-t_stat io_show_eiblks (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat io_show_eiblks (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fprintf (st, "eiblks=%d", ei_bmax);
 return SCPE_OK;
@@ -1358,7 +1358,7 @@ return;
 
 /* Set or show number of channels */
 
-t_stat io_set_nchan (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat io_set_nchan (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 i, num;
 t_stat r;
@@ -1378,7 +1378,7 @@ for (i = 0; i < CHAN_N_CHAN; i++) {
 return SCPE_OK;
 }
 
-t_stat io_show_nchan (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat io_show_nchan (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fprintf (st, "channels=%d", chan_num);
 return SCPE_OK;
@@ -1386,7 +1386,7 @@ return SCPE_OK;
 
 /* Set or show device channel assignment */
 
-t_stat io_set_dvc (UNIT* uptr, int32 val, char *cptr, void *desc)
+t_stat io_set_dvc (UNIT* uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 num;
 DEVICE *dptr;
@@ -1404,7 +1404,7 @@ dibp->dva = (dibp->dva & ~DVA_CHAN) | (num << DVA_V_CHAN);
 return SCPE_OK;
 }
 
-t_stat io_show_dvc (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat io_show_dvc (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 DEVICE *dptr;
 dib_t *dibp;
@@ -1418,7 +1418,7 @@ return SCPE_OK;
 
 /* Set or show device address */
 
-t_stat io_set_dva (UNIT* uptr, int32 val, char *cptr, void *desc)
+t_stat io_set_dva (UNIT* uptr, int32 val, CONST char *cptr, void *desc)
 {
 int32 num;
 DEVICE *dptr;
@@ -1439,7 +1439,7 @@ else dibp->dva = (dibp->dva & ~DVA_DEVSU) | ((num & DVA_M_DEVSU) << DVA_V_DEVSU)
 return SCPE_OK;
 }
 
-t_stat io_show_dva (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat io_show_dva (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 DEVICE *dptr;
 dib_t *dibp;
@@ -1453,7 +1453,7 @@ return SCPE_OK;
 
 /* Show channel state */
 
-t_stat io_show_cst (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat io_show_cst (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 DEVICE *dptr;
 dib_t *dibp;
diff --git a/sigma/sigma_io_defs.h b/sigma/sigma_io_defs.h
index f9bdf13e..6dedd093 100644
--- a/sigma/sigma_io_defs.h
+++ b/sigma/sigma_io_defs.h
@@ -260,17 +260,17 @@ uint32 chan_WrMemW (uint32 dva, uint32 dat);
 t_stat chan_reset_dev (uint32 dva);
 void io_sclr_req (uint32 inum, uint32 val);
 void io_sclr_arm (uint32 inum, uint32 val);
-t_stat io_set_dvc (UNIT* uptr, int32 val, char *cptr, void *desc);
-t_stat io_show_dvc (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat io_set_dva (UNIT* uptr, int32 val, char *cptr, void *desc);
-t_stat io_show_dva (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat io_show_cst (FILE *st, UNIT *uptr, int32 val, void *desc);
+t_stat io_set_dvc (UNIT* uptr, int32 val, CONST char *cptr, void *desc);
+t_stat io_show_dvc (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat io_set_dva (UNIT* uptr, int32 val, CONST char *cptr, void *desc);
+t_stat io_show_dva (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat io_show_cst (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 t_stat io_boot (int32 u, DEVICE *dptr);
 
 /* Internal real-time event scheduler */
 
-t_stat rtc_set_tps (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat rtc_show_tps (FILE *of, UNIT *uptr, int32 val, void *desc);
+t_stat rtc_set_tps (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat rtc_show_tps (FILE *of, UNIT *uptr, int32 val, CONST void *desc);
 t_stat rtc_register (uint32 tm, uint32 idx, UNIT *uptr);
 
 #endif
\ No newline at end of file
diff --git a/sigma/sigma_lp.c b/sigma/sigma_lp.c
index ceefb671..6d579adc 100644
--- a/sigma/sigma_lp.c
+++ b/sigma/sigma_lp.c
@@ -105,10 +105,10 @@ uint32 lp_tdv_status (void);
 t_stat lp_chan_err (uint32 st);
 t_stat lp_svc (UNIT *uptr);
 t_stat lp_reset (DEVICE *dptr);
-t_stat lp_attach (UNIT *uptr, char *cptr);
-t_stat lp_settype (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat lp_showtype (FILE *st, UNIT *uptr, int32 val, void *desc);
-t_stat lp_load_cct (UNIT *uptr, int32 val, char *cptr, void *desc);
+t_stat lp_attach (UNIT *uptr, CONST char *cptr);
+t_stat lp_settype (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat lp_showtype (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
+t_stat lp_load_cct (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
 t_stat lp_read_cct (FILE *cfile);
 uint32 lp_fmt (UNIT *uptr);
 uint32 lp_skip (UNIT *uptr, uint32 ch);
@@ -462,7 +462,7 @@ return SCPE_OK;
 
 /* Attach routine */
 
-t_stat lp_attach (UNIT *uptr, char *cptr)
+t_stat lp_attach (UNIT *uptr, CONST char *cptr)
 {
 lp_cctp = 0;                                            /* clear cct ptr */
 lp_pass = 0;
@@ -471,7 +471,7 @@ return attach_unit (uptr, cptr);
 
 /* Set handler for carriage control tape */
 
-t_stat lp_load_cct (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat lp_load_cct (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 FILE *cfile;
 t_stat r;
@@ -491,7 +491,7 @@ t_stat lp_read_cct (FILE *cfile)
 {
 uint32 col, rpt, ptr, mask;
 uint8 cctbuf[CCT_LNT];
-char *cptr;
+CONST char *cptr;
 t_stat r;
 char cbuf[CBUFSIZE], gbuf[CBUFSIZE];
 
@@ -529,7 +529,7 @@ return SCPE_OK;
 
 /* Set controller type */
 
-t_stat lp_settype (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat lp_settype (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 lp_model = val;
 lp_reset (&lp_dev);
@@ -538,7 +538,7 @@ return SCPE_OK;
 
 /* Show controller type */
 
-t_stat lp_showtype (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat lp_showtype (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fprintf (st, lp_model? "7450": "7440");
 return SCPE_OK;
diff --git a/sigma/sigma_mt.c b/sigma/sigma_mt.c
index 3395b07d..5dfa33c1 100644
--- a/sigma/sigma_mt.c
+++ b/sigma/sigma_mt.c
@@ -132,7 +132,7 @@ t_stat mt_chan_err (uint32 st);
 t_stat mtu_svc (UNIT *uptr);
 t_stat mtr_svc (UNIT *uptr);
 t_stat mt_reset (DEVICE *dptr);
-t_stat mt_attach (UNIT *uptr, char *cptr);
+t_stat mt_attach (UNIT *uptr, CONST char *cptr);
 t_stat mt_detach (UNIT *uptr);
 t_stat mt_flush_buf (UNIT *uptr);
 t_stat mt_map_err (UNIT *uptr, t_stat r);
@@ -336,12 +336,12 @@ r = SCPE_OK;
 switch (cmd) {                                          /* case on command */
 
     case MCM_SFWR:                                      /* space forward */
-        if (r = sim_tape_sprecf (uptr, &tbc))           /* spc rec fwd, err? */
+        if ((r = sim_tape_sprecf (uptr, &tbc)))         /* spc rec fwd, err? */
             r = mt_map_err (uptr, r);                   /* map error */
         break;
 
     case MCM_SBKR:                                      /* space reverse */
-        if (r = sim_tape_sprecr (uptr, &tbc))           /* spc rec rev, err? */
+        if ((r = sim_tape_sprecr (uptr, &tbc)))         /* spc rec rev, err? */
             r = mt_map_err (uptr, r);                   /* map error */
         break;
 
@@ -360,7 +360,7 @@ switch (cmd) {                                          /* case on command */
         break;
 
     case MCM_WTM:                                       /* write eof */
-        if (r = sim_tape_wrtmk (uptr))                  /* write tmk, err? */
+        if ((r = sim_tape_wrtmk (uptr)))                /* write tmk, err? */
             r = mt_map_err (uptr, r);                   /* map error */
         uptr->UST |= MTDV_EOF;                          /* set eof */
         break;
@@ -371,7 +371,7 @@ switch (cmd) {                                          /* case on command */
 
     case MCM_REW:                                       /* rewind */
     case MCM_RWI:                                       /* rewind and int */
-        if (r = sim_tape_rewind (uptr))                 /* rewind */
+        if ((r = sim_tape_rewind (uptr)))               /* rewind */
             r = mt_map_err (uptr, r);                   /* map error */
         mt_unit[un + MT_REW].UCMD = uptr->UCMD;         /* copy command */
         sim_activate (uptr + MT_REW, mt_rwtime);        /* sched compl */
@@ -461,7 +461,7 @@ t_stat st;
 
 if (mt_blim == 0)                                       /* any output? */
     return SCPE_OK;
-if (st = sim_tape_wrrecf (uptr, mt_xb, mt_blim))        /* write, err? */
+if ((st = sim_tape_wrrecf (uptr, mt_xb, mt_blim)))      /* write, err? */
     return mt_map_err (uptr, st);                       /* map error */
 return SCPE_OK;
 }
@@ -625,7 +625,7 @@ return SCPE_OK;
 
 /* Attach routine */
 
-t_stat mt_attach (UNIT *uptr, char *cptr)
+t_stat mt_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat r;
 
diff --git a/sigma/sigma_pt.c b/sigma/sigma_pt.c
index f5507f6b..cbda3052 100644
--- a/sigma/sigma_pt.c
+++ b/sigma/sigma_pt.c
@@ -1,6 +1,6 @@
 /* sigma_pt.c: Sigma 7060 paper tape reader/punch
 
-   Copyright (c) 2007-2008, Robert M. Supnik
+   Copyright (c) 2007-2018, Robert M. Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -24,6 +24,8 @@
    in this Software without prior written authorization from Robert M Supnik.
 
    pt           7060 paper-tape reader/punch
+
+   02-Jun-2018  RMS     Defanged clang signed/unsigned whining (Mark Pizzolato)
 */
 
 #include "sigma_io_defs.h"
@@ -61,7 +63,7 @@ uint32 pt_tdv_status (void);
 t_stat pt_chan_err (uint32 st);
 t_stat pt_svc (UNIT *uptr);
 t_stat pt_reset (DEVICE *dptr);
-t_stat pt_attach (UNIT *uptr, char *cptr);
+t_stat pt_attach (UNIT *uptr, CONST char *cptr);
 
 /* PT data structures
 
@@ -158,7 +160,7 @@ return 0;
 t_stat pt_svc (UNIT *uptr)
 {
 int32 c;
-uint32 cmd;
+uint32 uc, cmd;
 uint32 st;
 
 switch (pt_cmd) {                                       /* case on state */
@@ -196,7 +198,7 @@ switch (pt_cmd) {                                       /* case on state */
         if (c != 0)                                     /* leader done? */
             ptr_nzc = 1;                                /* set flag */
         if ((pt_cmd == PTS_READI) || ptr_nzc) {
-            st = chan_WrMemB (pt_dib.dva, c);           /* write to memory */
+            st = chan_WrMemB (pt_dib.dva, ((uint32) c));/* write to memory */
             if (CHS_IFERR (st))                         /* channel error? */
                 return pt_chan_err (st);
             if (st == CHS_ZBC)                          /* bc == 0? */
@@ -208,10 +210,10 @@ switch (pt_cmd) {                                       /* case on state */
         sim_activate (uptr, pt_unit[PTP].wait);         /* continue thread */
         if ((pt_unit[PTP].flags & UNIT_ATT) == 0)       /* not attached? */
             return ptp_stopioe? SCPE_UNATT: SCPE_OK;
-        st = chan_RdMemB (pt_dib.dva, &c);              /* read from channel */
+        st = chan_RdMemB (pt_dib.dva, &uc);             /* read from channel */
         if (CHS_IFERR (st))                             /* channel error? */
             return pt_chan_err (st);
-        if (putc (c, pt_unit[PTP].fileref) == EOF) {
+        if (putc (((int32) uc), pt_unit[PTP].fileref) == EOF) {
             perror ("PTP I/O error");
             clearerr (pt_unit[PTP].fileref);
             chan_set_chf (pt_dib.dva, CHF_XMDE);        /* data error */
@@ -286,7 +288,7 @@ return SCPE_OK;
 
 /* Attach routine */
 
-t_stat pt_attach (UNIT *uptr, char *cptr)
+t_stat pt_attach (UNIT *uptr, CONST char *cptr)
 {
 t_stat st;
 
diff --git a/sigma/sigma_rad.c b/sigma/sigma_rad.c
index 1b904a44..4c14ad31 100644
--- a/sigma/sigma_rad.c
+++ b/sigma/sigma_rad.c
@@ -124,8 +124,8 @@ uint32 rad_tdv_status (uint32 un);
 t_stat rad_chan_err (uint32 st);
 t_stat rad_svc (UNIT *uptr);
 t_stat rad_reset (DEVICE *dptr);
-t_stat rad_settype (UNIT *uptr, int32 val, char *cptr, void *desc);
-t_stat rad_showtype (FILE *st, UNIT *uptr, int32 val, void *desc);
+t_stat rad_settype (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
+t_stat rad_showtype (FILE *st, UNIT *uptr, int32 val, CONST void *desc);
 t_bool rad_inv_ad (uint32 *da);
 t_bool rad_inc_ad (void);
 t_bool rad_end_sec (UNIT *uptr, uint32 lnt, uint32 exp, uint32 st);
@@ -508,7 +508,7 @@ return SCPE_OK;
 
 /* Set controller type */
 
-t_stat rad_settype (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat rad_settype (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 i;
 
@@ -525,7 +525,7 @@ return SCPE_OK;
 
 /* Show controller type */
 
-t_stat rad_showtype (FILE *st, UNIT *uptr, int32 val, void *desc)
+t_stat rad_showtype (FILE *st, UNIT *uptr, int32 val, CONST void *desc)
 {
 fprintf (st, (rad_model == RAD_7212)? "7211/7212": "7231/7232");
 return SCPE_OK;
diff --git a/sigma/sigma_rtc.c b/sigma/sigma_rtc.c
index 1a97affc..08c13284 100644
--- a/sigma/sigma_rtc.c
+++ b/sigma/sigma_rtc.c
@@ -76,7 +76,7 @@ static rtcdef_t rtc_tab[RTC_NUM_HZ] = {
 t_stat rtc_svc (UNIT *uptr);
 t_stat rtc_cntr_svc (UNIT *uptr);
 t_stat rtc_reset (DEVICE *dptr);
-t_stat rtc_show_events (FILE *of, UNIT *uptr, int32 val, void *desc);
+t_stat rtc_show_events (FILE *of, UNIT *uptr, int32 val, CONST void *desc);
 
 /* Clock data structures
 
@@ -186,7 +186,7 @@ return SCPE_OK;
 
 /* Set timer ticks */
 
-t_stat rtc_set_tps (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat rtc_set_tps (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 uint32 newval, i;
 t_stat r;
@@ -214,7 +214,7 @@ return SCPE_ARG;
 
 /* Show timer ticks */
 
-t_stat rtc_show_tps (FILE *of, UNIT *uptr, int32 val, void *desc)
+t_stat rtc_show_tps (FILE *of, UNIT *uptr, int32 val, CONST void *desc)
 {
 uint32 idx;
 
@@ -255,7 +255,7 @@ return SCPE_OK;
 
 /* Show events */
 
-t_stat rtc_show_events (FILE *of, UNIT *uptr, int32 val, void *desc)
+t_stat rtc_show_events (FILE *of, UNIT *uptr, int32 val, CONST void *desc)
 {
 uint32 i;
 
diff --git a/sigma/sigma_sys.c b/sigma/sigma_sys.c
index 9a856dd8..95f5e8d2 100644
--- a/sigma/sigma_sys.c
+++ b/sigma/sigma_sys.c
@@ -49,7 +49,7 @@ extern uint32 *M;
 extern UNIT cpu_unit;
 
 t_stat fprint_sym_m (FILE *of, uint32 inst);
-t_stat parse_sym_m (char *cptr, t_value *val);
+t_stat parse_sym_m (CONST char *cptr, t_value *val);
 void fprint_ebcdic (FILE *of, uint32 c);
 
 extern t_stat lp_read_cct (FILE *cfile);
@@ -168,7 +168,7 @@ uint8 ebcdic_to_ascii[256] = {
 
 /* Binary loader */
 
-t_stat sim_load (FILE *fileref, char *cptr, char *fnam, int flag)
+t_stat sim_load (FILE *fileref, CONST char *cptr, CONST char *fnam, int flag)
 {
 return lp_read_cct (fileref);
 }
@@ -375,7 +375,7 @@ if (sw & SWMASK ('C')) {                                /* char format? */
 if (sw & SWMASK ('A')) {                                /* ASCII? */
     sc = 24 - ((addr & 0x3) * 8);                       /* shift count */
     c = (inst >> sc) & 0x7F;
-    fprintf (of, "%c", FMTASC (c));
+    fprintf (of, FMTASC (c));
     return 0;
     }
 if (sw & SWMASK ('E')) {                                /* EBCDIC? */
@@ -464,7 +464,7 @@ return;
         status  =       error status
 */
 
-t_stat parse_sym (char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
+t_stat parse_sym (CONST char *cptr, t_addr addr, UNIT *uptr, t_value *val, int32 sw)
 {
 t_value num;
 uint32 i, sc, rdx, c;
@@ -539,7 +539,7 @@ if (r != SCPE_OK)
 return 0;
 }
 
-t_stat parse_sym_m (char *cptr, t_value *val)
+t_stat parse_sym_m (CONST char *cptr, t_value *val)
 {
 uint32 i, sgn;
 t_stat r;
@@ -547,7 +547,7 @@ char *sep;
 char gbuf[CBUFSIZE];
 
 cptr = get_glyph (cptr, gbuf, 0);                       /* get opcode+reg*/
-if (sep = strchr (gbuf, ','))                           /* , in middle? */
+if ((sep = strchr (gbuf, ',')))                         /* , in middle? */
     *sep++ = 0;                                         /* split strings */
 for (i = 0; opcode[i] != NULL; i++) {                   /* loop thru ops */
     if (strcmp (opcode[i], gbuf) == 0) {                /* string match? */
@@ -583,7 +583,7 @@ for (i = 0; opcode[i] != NULL; i++) {                   /* loop thru ops */
                 sgn = 1;
             else sgn = 0;                               /* else + */
             cptr = get_glyph (cptr, gbuf, 0);           /* get rest */
-            if (sep = strchr (gbuf, ','))               /* , in middle? */
+            if ((sep = strchr (gbuf, ',')))             /* , in middle? */
                 *sep++ = 0;                             /* split strings */
             ad = get_uint (gbuf, 16, mask, &r);
             if (r != SCPE_OK)
diff --git a/sigma/sigma_tt.c b/sigma/sigma_tt.c
index 97d32d3c..1c357d2a 100644
--- a/sigma/sigma_tt.c
+++ b/sigma/sigma_tt.c
@@ -1,6 +1,6 @@
 /* sigma_tt.c: Sigma 7012 console teletype
 
-   Copyright (c) 2007-2008, Robert M. Supnik
+   Copyright (c) 2007-2018, Robert M. Supnik
 
    Permission is hereby granted, free of charge, to any person obtaining a
    copy of this software and associated documentation files (the "Software"),
@@ -30,6 +30,8 @@
    CR           input, mapped to NEWLINE and echoes CR-LF
    ^H           input, mapped to EOM and not echoed
    HT           input or output, simulates tabbing with fixed 8 character stops
+
+   02-Jun-2018  RMS     Defanged clang signed/unsigned whining (Mark Pizzolato)
 */
 
 #include "sigma_io_defs.h"
@@ -71,7 +73,7 @@ t_stat tti_rtc_svc (uint32 tm);
 t_stat tti_svc (UNIT *uptr);
 t_stat tto_svc (UNIT *uptr);
 t_stat tt_reset (DEVICE *dptr);
-t_stat tt_set_mode (UNIT *uptr, int32 val, char *cptr, void *desc);
+t_stat tt_set_mode (UNIT *uptr, int32 val, CONST char *cptr, void *desc);
 void tto_echo (int32 c);
 
 extern t_stat io_set_pint (void);
@@ -214,8 +216,8 @@ return SCPE_OK;
 
 t_stat tto_svc (UNIT *uptr)
 {
-int32 c, cmd;
-uint32 st;
+int32 c;
+uint32 uc, cmd, st;
 
 switch (tt_cmd) {                                       /* case on state */
 
@@ -231,10 +233,10 @@ switch (tt_cmd) {                                       /* case on state */
         break;
 
     case TTS_WRITE:                                     /* char output */
-        st = chan_RdMemB (tt_dib.dva, &c);              /* get char */
+        st = chan_RdMemB (tt_dib.dva, &uc);             /* get char */
         if (CHS_IFERR (st))                             /* channel error? */
             return tt_chan_err (st);
-        c = ebcdic_to_ascii[c & 0xFF];                  /* convert to ASCII */
+        c = ebcdic_to_ascii[uc & 0xFF];                 /* convert to ASCII */
         tto_echo (c);                                   /* echo character */
         sim_activate (uptr, uptr->wait);                /* continue thread */
         if (st == CHS_ZBC)                              /* st = zbc? */
@@ -321,7 +323,7 @@ return SCPE_OK;
 
 /* Make mode flags uniform */
 
-t_stat tt_set_mode (UNIT *uptr, int32 val, char *cptr, void *desc)
+t_stat tt_set_mode (UNIT *uptr, int32 val, CONST char *cptr, void *desc)
 {
 tt_unit[TTO].flags = (tt_unit[TTO].flags & ~TT_MODE) | val;
 if (val == TT_MODE_7P)