diff --git a/inc/commondefs.h b/inc/commondefs.h
index 17a3755..aab3035 100644
--- a/inc/commondefs.h
+++ b/inc/commondefs.h
@@ -1,8 +1,8 @@
 #ifndef COMMONDEFS_H
 #define COMMONDEFS_H 1
 void stab(void);
-void warn(char *s);
-int error(char *s);
+void warn(const char *s);
+int error(const char *s);
 int stackcheck(void);
 void stackoverflow(void);
 #endif
diff --git a/inc/ldsoutdefs.h b/inc/ldsoutdefs.h
index e97fbba..805146b 100644
--- a/inc/ldsoutdefs.h
+++ b/inc/ldsoutdefs.h
@@ -1,4 +1,4 @@
 #ifndef LDSOUTDEFS_H
 #define LDSOUTDEFS_H 1
-int sysout_loader(char * sysout_file_name, int sys_size);
+int sysout_loader(const char * sysout_file_name, int sys_size);
 #endif
diff --git a/inc/mkatomdefs.h b/inc/mkatomdefs.h
index e57ffe6..39a7ce8 100644
--- a/inc/mkatomdefs.h
+++ b/inc/mkatomdefs.h
@@ -1,11 +1,11 @@
 #ifndef MKATOMDEFS_H
 #define MKATOMDEFS_H 1
-DLword compute_hash(char *char_base, DLword offset, DLword length);
-DLword compute_lisp_hash(char *char_base, DLword offset, DLword length, DLword fatp);
-LispPTR compare_chars(register char *char1, register char *char2, register DLword length);
-int bytecmp(char *char1, char *char2, int len);
-LispPTR compare_lisp_chars(register char *char1, register char *char2, register DLword length, DLword fat1, DLword fat2);
-int lispcmp(DLword *char1, unsigned char *char2, int len);
-LispPTR make_atom(char *char_base, DLword offset, DLword length, short int non_numericp);
-LispPTR parse_number(char *char_base, short int length);
+DLword compute_hash(const char *char_base, DLword offset, DLword length);
+DLword compute_lisp_hash(const char *char_base, DLword offset, DLword length, DLword fatp);
+LispPTR compare_chars(register const char *char1, register const char *char2, register DLword length);
+int bytecmp(const char *char1, const char *char2, int len);
+LispPTR compare_lisp_chars(register const char *char1, register const char *char2, register DLword length, DLword fat1, DLword fat2);
+int lispcmp(const DLword *char1, const unsigned char *char2, int len);
+LispPTR make_atom(const char *char_base, DLword offset, DLword length, short int non_numericp);
+LispPTR parse_number(const char *char_base, short int length);
 #endif
diff --git a/inc/uraiddefs.h b/inc/uraiddefs.h
index 4edf67f..044927b 100644
--- a/inc/uraiddefs.h
+++ b/inc/uraiddefs.h
@@ -2,7 +2,7 @@
 #define URAIDDEFS_H 1
 LispPTR parse_atomstring(char *string);
 void uraid_commclear(void);
-void copy_region(DLword *src, DLword *dst, int width, int h);
+void copy_region(const DLword *src, DLword *dst, int width, int h);
 struct dtd *uGetDTD(unsigned int typenum);
 unsigned int uGetTN(unsigned int address);
 LispPTR uraid_commands(void);
diff --git a/inc/xrdoptdefs.h b/inc/xrdoptdefs.h
index c513541..d3bf21b 100644
--- a/inc/xrdoptdefs.h
+++ b/inc/xrdoptdefs.h
@@ -1,6 +1,6 @@
 #ifndef XRDOPTDEFS_H
 #define XRDOPTDEFS_H 1
-void print_Xusage(char *prog);
-void print_lispusage(char *prog);
+void print_Xusage(const char *prog);
+void print_lispusage(const char *prog);
 void read_Xoption(int *argc, char *argv[]);
 #endif
diff --git a/src/common.c b/src/common.c
index 603244c..d2e7a26 100644
--- a/src/common.c
+++ b/src/common.c
@@ -56,7 +56,7 @@ extern char URaid_comm;
 extern char URaid_arg1[256];
 extern char URaid_arg2[10];
 extern int URaid_argnum;
-extern char *URaid_errmess;
+extern const char *URaid_errmess;
 extern int URaid_currentFX;
 extern FX *URaid_FXarray[];
 extern jmp_buf BT_jumpbuf;
@@ -77,7 +77,7 @@ LispPTR Uraid_mess = NIL;
 /************************************************************************/
 
 #define URMAXCOMM 512
-int error(char *cp) {
+int error(const char *cp) {
   char *ptr;
   if (device_before_raid() < 0) {
     fprintf(stderr, "Can't Enter URAID.\n");
@@ -142,7 +142,7 @@ uraidloop:
 /*									*/
 /************************************************************************/
 
-void warn(char *s)
+void warn(const char *s)
 { printf("\nWARN: %s \n", s); }
 
 /*****************************************************************
diff --git a/src/ldsout.c b/src/ldsout.c
index f81251a..352819a 100644
--- a/src/ldsout.c
+++ b/src/ldsout.c
@@ -58,7 +58,7 @@ extern DspInterface currentdsp;
 #endif /* DOS || XWINDOW */
 
 /* sys_size is sysout size in megabytes */
-int sysout_loader(char * sysout_file_name, int sys_size)
+int sysout_loader(const char * sysout_file_name, int sys_size)
 {
   int sysout; /* SysoutFile descriptor */
 
diff --git a/src/mkatom.c b/src/mkatom.c
index a55676c..c280a3a 100644
--- a/src/mkatom.c
+++ b/src/mkatom.c
@@ -63,7 +63,7 @@ extern DLword *Lisp_world;
 */
 /**********************************************************************/
 
-DLword compute_hash(char *char_base, DLword offset, DLword length) {
+DLword compute_hash(const char *char_base, DLword offset, DLword length) {
   DLword hash;
   DLword number;
   DLword temp1;
@@ -94,7 +94,7 @@ DLword compute_hash(char *char_base, DLword offset, DLword length) {
 */
 /**********************************************************************/
 
-DLword compute_lisp_hash(char *char_base, DLword offset, DLword length, DLword fatp) {
+DLword compute_lisp_hash(const char *char_base, DLword offset, DLword length, DLword fatp) {
   DLword hash;
   DLword number;
   DLword temp1;
@@ -146,7 +146,7 @@ DLword compute_lisp_hash(char *char_base, DLword offset, DLword length, DLword f
 */
 /**********************************************************************/
 
-LispPTR compare_chars(register char *char1, register char *char2, register DLword length) {
+LispPTR compare_chars(register const char *char1, register const char *char2, register DLword length) {
 #ifndef BYTESWAP
   if (memcmp(char1, char2, length) == 0)
 #else
@@ -161,7 +161,7 @@ LispPTR compare_chars(register char *char1, register char *char2, register DLwor
 
 } /* end compare_chars */
 #ifdef BYTESWAP
-int bytecmp(char *char1, char *char2, int len)
+int bytecmp(const char *char1, const char *char2, int len)
 {
   int index;
   for (index = 0; index < len; index++) {
@@ -188,7 +188,7 @@ int bytecmp(char *char1, char *char2, int len)
 */
 /**********************************************************************/
 
-LispPTR compare_lisp_chars(register char *char1, register char *char2, register DLword length,
+LispPTR compare_lisp_chars(register const char *char1, register const char *char2, register DLword length,
                            DLword fat1, DLword fat2) {
   if ((!fat1) == (!fat2)) { /* both fat or both non-fat. */
 #ifdef BYTESWAP
@@ -231,7 +231,7 @@ LispPTR compare_lisp_chars(register char *char1, register char *char2, register
 
 } /* end compare_lisp_chars */
 
-int lispcmp(DLword *char1, unsigned char *char2, int len) {
+int lispcmp(const DLword *char1, const unsigned char *char2, int len) {
   int index;
   for (index = 0; index < len; index++) {
       if (GETWORD(char1++) != (unsigned char)GETBYTE(char2++)) return (0);
@@ -259,7 +259,7 @@ int lispcmp(DLword *char1, unsigned char *char2, int len) {
 */
 /**********************************************************************/
 
-LispPTR make_atom(char *char_base, DLword offset, DLword length, short int non_numericp)
+LispPTR make_atom(const char *char_base, DLword offset, DLword length, short int non_numericp)
 /* if it is NIL then these chars are treated as NUMBER */
 {
   extern DLword *Spospspace;
@@ -346,7 +346,7 @@ LispPTR make_atom(char *char_base, DLword offset, DLword length, short int non_n
 /*********************************************************************/
 
 /* Assume this func. should be called with C string in "char_base" */
-LispPTR parse_number(char *char_base, short int length) {
+LispPTR parse_number(const char *char_base, short int length) {
   register LispPTR sign_mask;
   register LispPTR val;
   register int radix;
diff --git a/src/uraid.c b/src/uraid.c
index 8a8f311..483bb7b 100644
--- a/src/uraid.c
+++ b/src/uraid.c
@@ -266,7 +266,7 @@ char URaid_comm;
 char URaid_arg1[URMAXCOMM / 2];
 char URaid_arg2[URMAXCOMM / 2];
 int URaid_argnum;
-char *URaid_errmess;
+const char *URaid_errmess;
 
 extern int PrintMaxLevel; /* for print level */
 
@@ -340,7 +340,7 @@ void uraid_commclear() {
   URaid_argnum = 0;
 }
 
-void copy_region(DLword *src, DLword *dst, int width, int h)
+void copy_region(const DLword *src, DLword *dst, int width, int h)
 {
   register int w;
 
diff --git a/src/xrdopt.c b/src/xrdopt.c
index 2fd73b9..199cc5c 100644
--- a/src/xrdopt.c
+++ b/src/xrdopt.c
@@ -113,7 +113,7 @@ extern struct sockaddr_nit snit;
 /*									*/
 /************************************************************************/
 
-void print_Xusage(char *prog)
+void print_Xusage(const char *prog)
 {
   fprintf(stderr, " %s options:\n", prog);
   fprintf(stderr, " [-sysout] [<sysout>]                 -path to the Medley image\n");
@@ -142,7 +142,7 @@ void print_Xusage(char *prog)
 /*									*/
 /************************************************************************/
 
-void print_lispusage(char *prog)
+void print_lispusage(const char *prog)
 {
   TPRINT(("TRACE: print_lisp_usage()\n"));