diff --git a/sim_BuildROMs.c b/sim_BuildROMs.c
index 8a3e6982..cebf2dfb 100644
--- a/sim_BuildROMs.c
+++ b/sim_BuildROMs.c
@@ -108,7 +108,7 @@ if ((expected_checksum != 0) && (checksum != expected_checksum)) {
  * If the target include file already exists, determine if it contains the exact
  * data in the base ROM image.  If so, then we are already done
  */
-if (iFile = fopen (include_filename, "r")) {
+if (NULL != (iFile = fopen (include_filename, "r"))) {
     unsigned char *IncludeData = NULL;
     char line[256];
     int Difference = 0;
diff --git a/sim_disk.c b/sim_disk.c
index 01613e53..a711a272 100644
--- a/sim_disk.c
+++ b/sim_disk.c
@@ -2550,13 +2550,13 @@ static FILE *sim_vhd_disk_open (const char *szVHDPath, const char *DesiredAccess
 
     if (!hVHD)
         return (FILE *)hVHD;
-    if (Status = GetVHDFooter (szVHDPath, 
-                               &hVHD->Footer, 
-                               &hVHD->Dynamic, 
-                               &hVHD->BAT,
-                               NULL,
-                               hVHD->ParentVHDPath,
-                               sizeof (hVHD->ParentVHDPath)))
+    if (0 != (Status = GetVHDFooter (szVHDPath, 
+                                     &hVHD->Footer, 
+                                     &hVHD->Dynamic, 
+                                     &hVHD->BAT,
+                                     NULL,
+                                     hVHD->ParentVHDPath,
+                                     sizeof (hVHD->ParentVHDPath))))
         goto Cleanup_Return;
     if (NtoHl (hVHD->Footer.DiskType) == VHD_DT_Differencing) {
         hVHD->Parent = (VHDHANDLE)sim_vhd_disk_open (hVHD->ParentVHDPath, "rb");
@@ -2702,7 +2702,7 @@ if (SizeInBytes > ((uint64)(1024*1024*1024))*2040) {
     Status = EFBIG;
     goto Cleanup_Return;
     }
-if (File = sim_fopen (szVHDPath, "rb")) {
+if (NULL != (File = sim_fopen (szVHDPath, "rb"))) {
     fclose (File);
     File = NULL;
     Status = EEXIST;
@@ -2877,13 +2877,13 @@ char *FullVHDPath = NULL;
 size_t i, RelativeMatch, UpDirectories, LocatorsWritten = 0;
 int64 LocatorPosition;
 
-if (Status = GetVHDFooter (szParentVHDPath, 
-                           &ParentFooter, 
-                           &ParentDynamic, 
-                           NULL, 
-                           &ParentTimeStamp,
-                           NULL, 
-                           0))
+if (0 != (Status = GetVHDFooter (szParentVHDPath, 
+                                 &ParentFooter, 
+                                 &ParentDynamic, 
+                                 NULL, 
+                                 &ParentTimeStamp,
+                                 NULL, 
+                                 0)))
     goto Cleanup_Return;
 hVHD = CreateVirtualDisk (szVHDPath,
                           (uint32)(NtoHll(ParentFooter.CurrentSize)/BytesPerSector),
diff --git a/sim_ether.c b/sim_ether.c
index 26641932..90d3bcd7 100644
--- a/sim_ether.c
+++ b/sim_ether.c
@@ -664,7 +664,7 @@ void eth_zero(ETH_DEV* dev)
 }
 
 static ETH_DEV **eth_open_devices = NULL;
-static eth_open_device_count = 0;
+static int eth_open_device_count = 0;
 
 static void _eth_add_to_open_list (ETH_DEV* dev)
 {
@@ -1394,7 +1394,7 @@ static void eth_get_nic_hw_addr(ETH_DEV* dev, char *devname)
     for (i=0; patterns[i] && (0 == dev->have_host_nic_phy_addr); ++i) {
       snprintf(command, sizeof(command)-1, "ifconfig %s | %s  >NIC.hwaddr", devname, patterns[i]);
       system(command);
-      if (f = fopen("NIC.hwaddr", "r")) {
+      if (NULL != (f = fopen("NIC.hwaddr", "r"))) {
         while (0 == dev->have_host_nic_phy_addr) {
           if (fgets(command, sizeof(command)-1, f)) {
             char *p1, *p2;
@@ -1580,7 +1580,7 @@ sim_debug(dev->dbit, dev->dptr, "Writer Thread Starting\n");
 pthread_mutex_lock (&dev->writer_lock);
 while (dev->handle) {
   pthread_cond_wait (&dev->writer_cond, &dev->writer_lock);
-  while (request = dev->write_requests) {
+  while (NULL != (request = dev->write_requests)) {
     /* Pull buffer off request list */
     dev->write_requests = request->next;
     pthread_mutex_unlock (&dev->writer_lock);
@@ -1889,11 +1889,11 @@ pthread_mutex_destroy (&dev->writer_lock);
 pthread_cond_destroy (&dev->writer_cond);
 if (1) {
   struct write_request *buffer;
-   while (buffer = dev->write_buffers) {
+   while (NULL != (buffer = dev->write_buffers)) {
     dev->write_buffers = buffer->next;
     free(buffer);
     }
-  while (buffer = dev->write_requests) {
+  while (NULL != (buffer = dev->write_requests)) {
     dev->write_requests = buffer->next;
     free(buffer);
     }
@@ -2146,10 +2146,10 @@ if (!dev) return SCPE_UNATT;
 
 /* Get a buffer */
 pthread_mutex_lock (&dev->writer_lock);
-if (request = dev->write_buffers)
+if (NULL != (request = dev->write_buffers))
   dev->write_buffers = request->next;
 pthread_mutex_unlock (&dev->writer_lock);
-if (!request)
+if (NULL == request)
   request = malloc(sizeof(*request));
 
 /* Copy buffer contents */
diff --git a/sim_tape.c b/sim_tape.c
index c6cbe410..2a28e133 100644
--- a/sim_tape.c
+++ b/sim_tape.c
@@ -761,7 +761,7 @@ t_stat st;
 sim_debug (ctx->dbit, ctx->dptr, "sim_tape_rdrecf(unit=%d, buf=%p, max=%d)\n", uptr-ctx->dptr->units, buf, max);
 
 opos = uptr->pos;                                       /* old position */
-if (st = sim_tape_rdlntf (uptr, &tbc))                  /* read rec lnt */
+if (MTSE_OK != (st = sim_tape_rdlntf (uptr, &tbc)))     /* read rec lnt */
     return st;
 *bc = rbc = MTR_L (tbc);                                /* strip error flag */
 if (rbc > max) {                                        /* rec out of range? */
@@ -823,7 +823,7 @@ t_stat st;
 
 sim_debug (ctx->dbit, ctx->dptr, "sim_tape_rdrecr(unit=%d, buf=%p, max=%d)\n", uptr-ctx->dptr->units, buf, max);
 
-if (st = sim_tape_rdlntr (uptr, &tbc))                  /* read rec lnt */
+if (MTSE_OK != (st = sim_tape_rdlntr (uptr, &tbc)))     /* read rec lnt */
     return st;
 *bc = rbc = MTR_L (tbc);                                /* strip error flag */
 if (rbc > max)                                          /* rec out of range? */