diff --git a/dos/pdcclip.c b/dos/pdcclip.c
index 32403779..34b051f9 100644
--- a/dos/pdcclip.c
+++ b/dos/pdcclip.c
@@ -16,7 +16,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-RCSID("$Id: pdcclip.c,v 1.25 2006/10/15 02:42:25 wmcbrine Exp $");
+RCSID("$Id: pdcclip.c,v 1.26 2006/11/05 05:37:40 wmcbrine Exp $");
 
 /* global clipboard contents, should be NULL if none set */
 
@@ -54,7 +54,7 @@ int PDC_getclipboard(char **contents, long *length)
 
 	PDC_LOG(("PDC_getclipboard() - called\n"));
 
-	if (pdc_DOS_clipboard == NULL)
+	if (!pdc_DOS_clipboard)
 		return PDC_CLIP_EMPTY;
 
 	len = strlen(pdc_DOS_clipboard);
@@ -93,13 +93,13 @@ int PDC_setclipboard(const char *contents, long length)
 {
 	PDC_LOG(("PDC_setclipboard() - called\n"));
 
-	if (pdc_DOS_clipboard != NULL) 
+	if (pdc_DOS_clipboard)
 	{
 		free(pdc_DOS_clipboard);
 		pdc_DOS_clipboard = NULL;
 	}
 
-	if (contents != NULL)
+	if (contents)
 	{
 		if ((pdc_DOS_clipboard = malloc(length + 1)) == NULL)
 			return PDC_CLIP_MEMORY_ERROR;
@@ -134,7 +134,7 @@ int PDC_freeclipboard(char *contents)
 
 	/* should we also free empty the system clipboard? probably not */
 
-	if (contents != NULL)
+	if (contents)
 	{
 		/* NOTE: We free the memory, but we can not set caller's 
 		   pointer to NULL, so if caller calls again then will 
@@ -174,7 +174,7 @@ int PDC_clearclipboard(void)
 {
 	PDC_LOG(("PDC_clearclipboard() - called\n"));
 
-	if (pdc_DOS_clipboard != NULL) 
+	if (pdc_DOS_clipboard) 
 	{
 		free(pdc_DOS_clipboard);
 		pdc_DOS_clipboard = NULL;
diff --git a/dos/pdcgetsc.c b/dos/pdcgetsc.c
index b6fea606..ef2dd601 100644
--- a/dos/pdcgetsc.c
+++ b/dos/pdcgetsc.c
@@ -15,7 +15,7 @@
 
 #include <stdlib.h>
 
-RCSID("$Id: pdcgetsc.c,v 1.34 2006/10/15 02:42:25 wmcbrine Exp $");
+RCSID("$Id: pdcgetsc.c,v 1.35 2006/11/05 05:37:40 wmcbrine Exp $");
 
 /*man-start**************************************************************
 
@@ -140,7 +140,7 @@ int PDC_get_cursor_mode(void)
 
 int PDC_get_rows(void)
 {
-	char *env_rows;
+	const char *env_rows;
 	int rows;
 
 	PDC_LOG(("PDC_get_rows() - called\n"));
@@ -149,14 +149,14 @@ int PDC_get_rows(void)
  /* and use the minimum of LINES and *ROWS.                MH 18-Jun-92 */
 
 	rows = getdosmembyte(0x484) + 1;
-	env_rows = (char *)getenv("LINES");
+	env_rows = getenv("LINES");
 
-	if (env_rows != (char *)NULL)
+	if (env_rows)
 		rows = min(atoi(env_rows), rows);
 
-	if ((rows == 1) && (pdc_adapter == _MDS_GENIUS))
+	if (rows == 1 && pdc_adapter == _MDS_GENIUS)
 		rows = 66;
-	if ((rows == 1) && (pdc_adapter == _MDA))
+	if (rows == 1 && pdc_adapter == _MDA)
 		rows = 25;
 
 	if (rows == 1)
diff --git a/dos/pdcscrn.c b/dos/pdcscrn.c
index 30573124..cb4d0b37 100644
--- a/dos/pdcscrn.c
+++ b/dos/pdcscrn.c
@@ -20,7 +20,7 @@
 # include <sys/movedata.h>
 #endif
 
-RCSID("$Id: pdcscrn.c,v 1.66 2006/10/28 13:26:01 wmcbrine Exp $");
+RCSID("$Id: pdcscrn.c,v 1.67 2006/11/05 05:37:40 wmcbrine Exp $");
 
 int	pdc_adapter;		/* screen type				*/
 int	pdc_scrnmode;		/* default screen mode			*/
@@ -470,7 +470,7 @@ void PDC_scr_close(void)
 #endif
 	PDC_LOG(("PDC_scr_close() - called\n"));
 
-	if ((getenv("PDC_RESTORE_SCREEN") != NULL) && (saved_screen != NULL))
+	if (getenv("PDC_RESTORE_SCREEN") && saved_screen)
 	{
 #ifdef __DJGPP__
 		dosmemput(saved_screen, saved_lines * saved_cols * 2,
@@ -566,12 +566,12 @@ int PDC_scr_open(int argc, char **argv)
 	   int10() BIOS calls are used in place of direct video memory 
 	   access. */
 
-	if (getenv("PDCURSES_BIOS") != NULL)
+	if (getenv("PDCURSES_BIOS"))
 		pdc_direct_video = FALSE;
 
 	/* This code for preserving the current screen. */
 
-	if (getenv("PDC_RESTORE_SCREEN") != NULL)
+	if (getenv("PDC_RESTORE_SCREEN"))
 	{
 		saved_lines = SP->lines;
 		saved_cols = SP->cols;
diff --git a/os2/pdcgetsc.c b/os2/pdcgetsc.c
index be5c0c17..c4f7c476 100644
--- a/os2/pdcgetsc.c
+++ b/os2/pdcgetsc.c
@@ -13,7 +13,7 @@
 
 #include "pdcos2.h"
 
-RCSID("$Id: pdcgetsc.c,v 1.31 2006/10/15 02:42:25 wmcbrine Exp $");
+RCSID("$Id: pdcgetsc.c,v 1.32 2006/11/05 05:37:40 wmcbrine Exp $");
 
 /*man-start**************************************************************
 
@@ -79,7 +79,7 @@ int PDC_get_columns(void)
 	VIOMODEINFO modeInfo = {0};
 #endif
 	int cols = 0;
-	char *env_cols = NULL;
+	const char *env_cols;
 
 	PDC_LOG(("PDC_get_columns() - called\n"));
 
@@ -90,9 +90,9 @@ int PDC_get_columns(void)
 	VioGetMode(&modeInfo, 0);
 	cols = modeInfo.col;
 #endif
-	env_cols = (char *)getenv("COLS");
+	env_cols = getenv("COLS");
 
-	if (env_cols != (char *)NULL)
+	if (env_cols)
 		cols = min(atoi(env_cols), cols);
 
 	PDC_LOG(("PDC_get_columns() - returned: cols %d\n", cols));
@@ -157,7 +157,7 @@ int PDC_get_rows(void)
 	VIOMODEINFO modeInfo = {0};
 #endif
 	int rows = 0;
-	char *env_rows = NULL;
+	const char *env_rows;
 
 	PDC_LOG(("PDC_get_rows() - called\n"));
 
@@ -171,9 +171,9 @@ int PDC_get_rows(void)
 	VioGetMode(&modeInfo, 0);
 	rows = modeInfo.row;
 #endif
-	env_rows = (char *)getenv("LINES");
+	env_rows = getenv("LINES");
 
-	if (env_rows != (char *)NULL)
+	if (env_rows)
 		rows = min(atoi(env_rows), rows);
 
 	PDC_LOG(("PDC_get_rows() - returned: rows %d\n", rows));
diff --git a/os2/pdcscrn.c b/os2/pdcscrn.c
index 1385376d..e691a2e7 100644
--- a/os2/pdcscrn.c
+++ b/os2/pdcscrn.c
@@ -13,7 +13,7 @@
 
 #include "pdcos2.h"
 
-RCSID("$Id: pdcscrn.c,v 1.57 2006/10/18 23:09:16 wmcbrine Exp $");
+RCSID("$Id: pdcscrn.c,v 1.58 2006/11/05 05:37:40 wmcbrine Exp $");
 
 int pdc_font;			/* default font size	*/
 
@@ -94,7 +94,7 @@ void PDC_scr_close(void)
 	if (DosScanEnv("PDC_RESTORE_SCREEN", (PSZ *)&ptr))
 		ptr = NULL;
 #endif
-	if ((ptr != NULL) && (saved_screen != NULL))
+	if (ptr && saved_screen)
 	{
 #ifdef EMXVIDEO
 		v_putline(saved_screen, 0, 0, saved_lines * saved_cols);
diff --git a/win32/pdcclip.c b/win32/pdcclip.c
index 150b25af..095e5eb3 100644
--- a/win32/pdcclip.c
+++ b/win32/pdcclip.c
@@ -13,7 +13,7 @@
 
 #include "pdcwin.h"
 
-RCSID("$Id: pdcclip.c,v 1.20 2006/10/15 02:42:26 wmcbrine Exp $");
+RCSID("$Id: pdcclip.c,v 1.21 2006/11/05 05:37:40 wmcbrine Exp $");
 
 /*man-start**************************************************************
 
@@ -49,12 +49,10 @@ int PDC_getclipboard(char **contents, long *length)
 
 	PDC_LOG(("PDC_getclipboard() - called\n"));
 
-	if (OpenClipboard(NULL) == 0)
+	if (!OpenClipboard(NULL))
 		return PDC_CLIP_ACCESS_ERROR;
 
-	handle = GetClipboardData(CF_TEXT);
-
-	if (handle == NULL)
+	if ((handle = GetClipboardData(CF_TEXT)) == NULL)
 	{
 		CloseClipboard();
 		return PDC_CLIP_EMPTY;
@@ -104,7 +102,7 @@ int PDC_setclipboard(const char *contents, long length)
 
 	PDC_LOG(("PDC_setclipboard() - called\n"));
 
-	if (OpenClipboard(NULL) == 0)
+	if (!OpenClipboard(NULL))
 		return PDC_CLIP_ACCESS_ERROR;
 
 	ptr1 = GlobalAlloc(GMEM_MOVEABLE|GMEM_DDESHARE, 
@@ -119,7 +117,7 @@ int PDC_setclipboard(const char *contents, long length)
 	GlobalUnlock(ptr1);
 	EmptyClipboard();
 
-	if (SetClipboardData(CF_TEXT, ptr1) == NULL)
+	if (!SetClipboardData(CF_TEXT, ptr1))
 	{
 		GlobalFree(ptr1);
 		return PDC_CLIP_ACCESS_ERROR;
diff --git a/win32/pdcscrn.c b/win32/pdcscrn.c
index b017fe32..5c4ed7e5 100644
--- a/win32/pdcscrn.c
+++ b/win32/pdcscrn.c
@@ -13,7 +13,7 @@
 
 #include "pdcwin.h"
 
-RCSID("$Id: pdcscrn.c,v 1.68 2006/10/18 23:09:16 wmcbrine Exp $");
+RCSID("$Id: pdcscrn.c,v 1.69 2006/11/05 05:37:40 wmcbrine Exp $");
 
 #define PDC_RESTORE_NONE     0
 #define PDC_RESTORE_BUFFER   1
@@ -354,7 +354,7 @@ int PDC_scr_open(int argc, char **argv)
 
 	SP->_restore = PDC_RESTORE_NONE;
 
-	if (getenv("PDC_RESTORE_SCREEN") != NULL)
+	if (getenv("PDC_RESTORE_SCREEN"))
 	{
 		/* Attempt to save the complete console buffer */
 
diff --git a/x11/pdcscrn.c b/x11/pdcscrn.c
index fc680c91..efa269d5 100644
--- a/x11/pdcscrn.c
+++ b/x11/pdcscrn.c
@@ -13,7 +13,7 @@
 
 #include "pdcx11.h"
 
-RCSID("$Id: pdcscrn.c,v 1.45 2006/10/18 23:09:16 wmcbrine Exp $");
+RCSID("$Id: pdcscrn.c,v 1.46 2006/11/05 05:37:40 wmcbrine Exp $");
 
 /*man-start**************************************************************
 
@@ -66,7 +66,7 @@ int PDC_scr_open(int argc, char **argv)
 
 	PDC_LOG(("PDC_scr_open() - called\n"));
 
-	if ((XCursesInitscr(argc, argv) == ERR) || (SP == (SCREEN *)NULL))
+	if ((XCursesInitscr(argc, argv) == ERR) || !SP)
 		return ERR;
 
 	SP->cursrow = SP->curscol = 0;
diff --git a/x11/pdcx11.c b/x11/pdcx11.c
index 958b2a57..5d144139 100644
--- a/x11/pdcx11.c
+++ b/x11/pdcx11.c
@@ -15,7 +15,7 @@
 
 #include <stdlib.h>
 
-RCSID("$Id: pdcx11.c,v 1.87 2006/10/15 02:42:26 wmcbrine Exp $");
+RCSID("$Id: pdcx11.c,v 1.88 2006/11/05 05:37:40 wmcbrine Exp $");
 
 
 /*** Functions that are called by both processes ***/
@@ -239,7 +239,7 @@ int XCursesInitscr(int argc, char *argv[])
 	XC_LOG(("XCursesInitscr() - called\n"));
 
 #if defined FOREIGN
-	if (setlocale(LC_ALL, "") == NULL)
+	if (!setlocale(LC_ALL, ""))
 	{
 		fprintf(stderr, "ERROR: cannot set locale\n");
 		return ERR;
@@ -251,7 +251,7 @@ int XCursesInitscr(int argc, char *argv[])
 		return ERR;
 	}
 
-	if (XSetLocaleModifiers("") == NULL)
+	if (!XSetLocaleModifiers(""))
 		fprintf(stderr, "WARNING: Cannot set locale modifiers\n");
 #endif
 	shmkeySP = getpid();
diff --git a/x11/x11.c b/x11/x11.c
index d626adf1..c6e07ee9 100644
--- a/x11/x11.c
+++ b/x11/x11.c
@@ -28,7 +28,7 @@
 #include <stdlib.h>
 #include <string.h>
 
-RCSID("$Id: x11.c,v 1.28 2006/10/28 13:26:01 wmcbrine Exp $");
+RCSID("$Id: x11.c,v 1.29 2006/11/05 05:37:40 wmcbrine Exp $");
 
 #ifndef XPOINTER_TYPEDEFED
 typedef char * XPointer;
@@ -661,7 +661,7 @@ static Atom XA_UTF8_STRING(Display *dpy)
 {
 	static AtomPtr p = NULL;
 
-	if (p == NULL)
+	if (!p)
 		p = XmuMakeAtom("UTF8_STRING");
 
 	return XmuInternAtom(dpy, p);
@@ -1029,7 +1029,7 @@ static void GetIcon(void)
 	XFree((char *)icon_size);
 
 #ifdef HAVE_XPM_H
-	if (strcmp(xc_app_data.pixmap, "") != 0) /* supplied pixmap */
+	if (xc_app_data.pixmap && xc_app_data.pixmap[0]) /* supplied pixmap */
 	{
 		XpmReadFileToPixmap(XtDisplay(topLevel),
 			RootWindowOfScreen(XtScreen(topLevel)),
@@ -1039,7 +1039,7 @@ static void GetIcon(void)
 	}
 #endif
 
-	if (strcmp(xc_app_data.bitmap, "") != 0) /* supplied bitmap */
+	if (xc_app_data.bitmap && xc_app_data.bitmap[0]) /* supplied bitmap */
 	{
 		int x_hot = 0, y_hot = 0;
 
@@ -1558,7 +1558,7 @@ static void RequestorCallbackForPaste(Widget w, XtPointer data,
 
 	XC_LOG(("RequestorCallbackForPaste() - called\n"));
 
-	if ((value == NULL) && (*length == 0))
+	if (!string)
 		return;
 
 	for (i = 0; i < (*length); i++)
@@ -2080,7 +2080,7 @@ static void SendKeyToCurses(unsigned long key, MOUSE_STATUS *ms)
 		ExitProcess(1, SIGKILL, "exiting from SendKeyToCurses");
 	}
 
-	if (ms != NULL)
+	if (ms)
 	{
 		MOUSE_LOG(("%s:writing mouse stuff\n", XCLOGMSG));
 
@@ -2557,14 +2557,14 @@ static void ExitProcess(int rc, int sig, char *msg)
 	shmctl(shmidSP, IPC_RMID, 0);
 	shmctl(shmid_Xcurscr, IPC_RMID, 0);
 
-	if (bitmap_file != NULL)
+	if (bitmap_file)
 	{
 		XFreePixmap(XCURSESDISPLAY, icon_bitmap);
 		free(bitmap_file);
 	}
 
 #ifdef HAVE_XPM_H
-	if (pixmap_file != NULL)
+	if (pixmap_file)
 	{
 		XFreePixmap(XCURSESDISPLAY, icon_pixmap);
 		XFreePixmap(XCURSESDISPLAY, icon_pixmap_mask);
@@ -2978,7 +2978,7 @@ int XCursesSetupX(int argc, char *argv[])
 
 	/* Exit if no DISPLAY variable set */
 
-	if (getenv("DISPLAY") == NULL)
+	if (!getenv("DISPLAY"))
 	{
 		fprintf(stderr, "Error: no DISPLAY variable set\n");
 		kill(xc_otherpid, SIGKILL);
@@ -3035,8 +3035,7 @@ int XCursesSetupX(int argc, char *argv[])
 	GetIcon();
 
 #ifdef HAVE_XPM_H
-	if (xc_app_data.pixmap != NULL &&
-	    strcmp(xc_app_data.pixmap, "") != 0)
+	if (xc_app_data.pixmap && xc_app_data.pixmap[0])
 		XtVaSetValues(topLevel, XtNminWidth, minwidth, XtNminHeight,
 			minheight, XtNbaseWidth, xc_app_data.borderWidth * 2,
 			XtNbaseHeight, xc_app_data.borderWidth * 2,
@@ -3378,7 +3377,7 @@ static void RequestorCallbackForGetSelection(Widget w, XtPointer data,
 {
 	XC_LOG(("RequestorCallbackForGetSelection() - called\n"));
 
-	if ((value == NULL) && (*length == 0))
+	if (!value && !(*length))
 	{
 	    if (XC_write_display_socket_int(PDC_CLIP_EMPTY) >= 0)
 		return;