diff --git a/scp.c b/scp.c
index 0b455787..1cfaf001 100644
--- a/scp.c
+++ b/scp.c
@@ -4614,7 +4614,7 @@ char gbuf[CBUFSIZE];
 char *ip = instr, *op, *oend, *istart, *tmpbuf;
 const char *ap;
 char rbuf[CBUFSIZE];
-int i;
+uint32 i;
 size_t outstr_off = 0;
 
 sim_exp_argv = do_arg;
@@ -4677,7 +4677,7 @@ for (; *ip && (op < oend); ) {
                 }
             if ((*ip >= '0') && (*ip <= ('9'))) {       /* %n = sub */
                 ap = do_arg[*ip - '0'];
-                for (i=0; i<*ip - '0'; ++i)           /* make sure we're not past the list end */
+                for (i=0; i < (uint32)(*ip - '0'); ++i) /* make sure we're not past the list end */
                     if (do_arg[i] == NULL) {
                         ap = NULL;
                         break;
@@ -9664,7 +9664,7 @@ void put_rval_pcchk (REG *rptr, uint32 idx, t_value val, t_bool pc_chk)
 size_t sz;
 t_value mask;
 uint32 *ptr;
-t_value prev_val;
+t_value prev_val = 0;
 
 if ((!(sim_switches & SWMASK ('Z'))) && 
     (rptr->flags & REG_DEPOSIT) && sim_vm_reg_update)
@@ -11125,7 +11125,7 @@ for (logop = cmpop = -1; (c = *cptr++); ) {             /* loop thru clauses */
         return NULL;
         }
     }                                                   /* end for */
-if (schptr->count != (1 - reason)) {
+if (schptr->count != (uint32)(1 - reason)) {
     schptr->count = 1 - reason;
     free (schptr->mask);
     schptr->mask = (t_value *)calloc (sim_emax, sizeof(*schptr->mask));
@@ -12221,7 +12221,7 @@ bp = sim_brk_fnd (loc);                                 /* loc present? */
 if (!bp)                                                /* no, allocate */
     bp = sim_brk_new (loc, sw);
 else {
-    while (bp && (bp->typ != sw))
+    while (bp && (bp->typ != (uint32)sw))
         bp = bp->next;
     if (!bp)
         bp = sim_brk_new (loc, sw);
@@ -14106,7 +14106,7 @@ static volatile struct {
     size_t block;
     size_t line;
     } help_where = { "", NULL, 0, 0 };
-jmp_buf (help_env);
+jmp_buf help_env;
 #define FAIL(why,text,here) { help_where.error = #text; help_where.prox = here; longjmp (help_env, (why)); }
 
 /* Add to topic text.
@@ -15889,7 +15889,7 @@ static struct validation_test {
             { ORDATAD (REGVAL, tregval, 8*sizeof(tregval), "value register") },
             {NULL} },
          SCPE_OK},
-        {NULL}
+        { { {NULL} } }
     };
 
 static UNIT validate_units[3];
@@ -16047,7 +16047,7 @@ static t_stat test_scp_event_sequencing (void)
 {
 DEVICE *dptr = &sim_scp_dev;
 uint32 i;
-int active;
+uint32 active;
 t_stat r = SCPE_OK;
 int32 start_deb_switches = sim_set_deb_switches (0);
 
@@ -16071,7 +16071,7 @@ for (i = 0; i < dptr->numunits; i++) {
 for (i = 0; i < dptr->numunits; i++) {
     int32 t = sim_activate_time (&dptr->units[i]);
 
-    if (t != i + 1)
+    if (t != (int32)(i + 1))
         return sim_messagef (SCPE_IERR, "sim_activate_time() unexpected result for unit %d: %d\n", i, t);
     }
 sim_printf ("sim_interval = %d, sim_gtime = %.0f\n", sim_interval, sim_gtime ());
@@ -16081,7 +16081,7 @@ sim_printf ("sim_interval = %d, sim_gtime = %.0f\n", sim_interval, sim_gtime ())
 for (i = 0; i < dptr->numunits; i++) {
     int32 t = sim_activate_time (&dptr->units[i]);
 
-    if (t != i + 1)
+    if (t != (int32)(i + 1))
         return sim_messagef (SCPE_IERR, "sim_activate_time() unexpected result for unit %d: %d\n", i, t);
     }
 r = sim_process_event ();
diff --git a/sim_disk.c b/sim_disk.c
index 4540ad09..5b7751f5 100644
--- a/sim_disk.c
+++ b/sim_disk.c
@@ -2145,7 +2145,7 @@ sim_debug_unit (ctx->dbit, uptr, "get_disk_footer(%s)\n", sim_uname (uptr));
 switch (DK_GET_FMT (uptr)) {                            /* case on format */
     case DKUF_F_STD:                                    /* SIMH format */
         container_size = sim_fsize_ex (uptr->fileref);
-        if ((container_size != (t_offset)-1) && (container_size > sizeof (*f)) &&
+        if ((container_size != (t_offset)-1) && (container_size > (t_offset)sizeof (*f)) &&
             (sim_fseeko (uptr->fileref, container_size - sizeof (*f), SEEK_SET) == 0) &&
             (sizeof (*f) == sim_fread (f, 1, sizeof (*f), uptr->fileref)))
             break;
@@ -2154,7 +2154,7 @@ switch (DK_GET_FMT (uptr)) {                            /* case on format */
         break;
     case DKUF_F_RAW:                                    /* RAW format */
         container_size = sim_os_disk_size_raw (uptr->fileref);
-        if ((container_size != (t_offset)-1) && (container_size > sizeof (*f)) &&
+        if ((container_size != (t_offset)-1) && (container_size > (t_offset)sizeof (*f)) &&
             (sim_os_disk_read (uptr, container_size - sizeof (*f), (uint8 *)f, &bytesread, sizeof (*f)) == SCPE_OK) &&
             (bytesread == sizeof (*f)))
             break;
@@ -3944,12 +3944,12 @@ while (bytestoread) {
     if (bytesread < 0) {
         return SCPE_IOERR;
         }
-    if (bytesread < bytestoread) {      /* read zeros at/past EOF */
+    if ((size_t)bytesread < bytestoread) {/* read zeros at/past EOF */
         memset (buf + bytesread, 0, bytestoread - bytesread);
         bytesread = bytestoread;
         }
     sectorbytes = (bytesread / ctx->sector_size) * ctx->sector_size;
-    if (bytesread > sectorbytes)
+    if ((size_t)bytesread > sectorbytes)
         sectorbytes += ctx->sector_size;
     if (sectsread)
         *sectsread += sectorbytes / ctx->sector_size;
@@ -6034,7 +6034,7 @@ if (info->flag) {        /* zap type */
         return;
         }
     container_size = sim_fsize_ex (container);
-    if ((container_size != (t_offset)-1) && (container_size > sizeof (*f)) &&
+    if ((container_size != (t_offset)-1) && (container_size > (t_offset)sizeof (*f)) &&
         (sim_fseeko (container, container_size - sizeof (*f), SEEK_SET) == 0) &&
         (sizeof (*f) == sim_fread (f, 1, sizeof (*f), container))) {
         if ((memcmp (f->Signature, "simh", 4) == 0) && 
diff --git a/sim_fio.c b/sim_fio.c
index 4d76dc4a..8b297b7d 100644
--- a/sim_fio.c
+++ b/sim_fio.c
@@ -724,7 +724,7 @@ else {
     struct stat statb;
 
     if ((fstat ((*shmem)->shm_fd, &statb)) ||
-        (statb.st_size != (*shmem)->shm_size)) {
+        ((size_t)statb.st_size != (*shmem)->shm_size)) {
         sim_shmem_close (*shmem);
         *shmem = NULL;
         return sim_messagef (SCPE_OPENERR, "Shared Memory segment '%s' is %d bytes instead of %d\n", name, (int)(statb.st_size), (int)size);
diff --git a/sim_tape.c b/sim_tape.c
index c46db1d7..56329019 100644
--- a/sim_tape.c
+++ b/sim_tape.c
@@ -4463,7 +4463,7 @@ static void ansi_fill_text_buffer (FILE *f, char *buf, size_t buf_size, size_t r
         if (!fixed_text) {
             if (rec_size >= record_skip_ending)
                 rec_size -= record_skip_ending;
-            if ((rec_size + 4) > (int)(buf_size - offset)) { /* room for record? */
+            if ((rec_size + 4) > (buf_size - offset)) { /* room for record? */
                 (void)fseek (f, start, SEEK_SET);
                 break;
                 }
diff --git a/sim_tmxr.c b/sim_tmxr.c
index c346f521..43f05e86 100644
--- a/sim_tmxr.c
+++ b/sim_tmxr.c
@@ -5706,11 +5706,11 @@ return SCPE_OK;
 
 static t_stat sim_tmxr_test_lnorder (TMXR *tmxr)
 {
-int i;
+uint32 i;
 int32 *saved_lnorder = tmxr->lnorder;
 int32 saved_lines = tmxr->lines;
 
-tmxr->lnorder = calloc (tmxr->lines, sizeof (*tmxr->lnorder));
+tmxr->lnorder = (int32 *)calloc (tmxr->lines, sizeof (*tmxr->lnorder));
 if (tmxr->lines >= 8) {
     tmxr->lines = 8;
     for (i = 0; i < (sizeof (lnorders)/sizeof (lnorders[0])); ++i)
diff --git a/sim_video.c b/sim_video.c
index 3da55057..ccbf1d26 100644
--- a/sim_video.c
+++ b/sim_video.c
@@ -118,7 +118,7 @@ static const char *key_names[] =
      "KP_INSERT", "KP_DELETE", "KP_5", "KP_ENTER", "KP_MULTIPLY", "KP_DIVIDE"
      };
 
-const char *vid_key_name (int32 key)
+const char *vid_key_name (uint32 key)
 {
 static char tmp_key_name[40];
 
@@ -942,7 +942,7 @@ if (sim_deb) {
             int bit = 7 - ((j + i*width) & 0x7);
             static char mode[] = "TWIB";
 
-            sim_debug (SIM_VID_DBG_CURSOR, vptr->vid_dev, "%c", mode[(((data[byte]>>bit)&1)<<1)|(mask[byte]>>bit)&1]);
+            sim_debug (SIM_VID_DBG_CURSOR, vptr->vid_dev, "%c", mode[(((data[byte]>>bit)&1)<<1)|((mask[byte]>>bit)&1)]);
             }
         sim_debug (SIM_VID_DBG_CURSOR, vptr->vid_dev, "\n");
         }
@@ -2794,7 +2794,7 @@ void vid_set_cursor_position_window (VID_DISPLAY *vptr, int32 x, int32 y)
 return;
 }
 
-const char *vid_key_name (int32 key)
+const char *vid_key_name (uint32 key)
 {
 return "";
 }
diff --git a/sim_video.h b/sim_video.h
index 3127b453..0d6882f1 100644
--- a/sim_video.h
+++ b/sim_video.h
@@ -202,7 +202,7 @@ void vid_draw (int32 x, int32 y, int32 w, int32 h, uint32 *buf);
 void vid_beep (void);
 void vid_refresh (void);
 const char *vid_version (void);
-const char *vid_key_name (int32 key);
+const char *vid_key_name (uint32 key);
 t_stat vid_set_cursor (t_bool visible, uint32 width, uint32 height, uint8 *data, uint8 *mask, uint32 hot_x, uint32 hot_y);
 t_stat vid_set_release_key (FILE* st, UNIT* uptr, int32 val, CONST void* desc);
 t_stat vid_show_release_key (FILE* st, UNIT* uptr, int32 val, CONST void* desc);