diff --git a/include/epanet2.h b/include/epanet2.h
index dd99410..dc3d362 100644
--- a/include/epanet2.h
+++ b/include/epanet2.h
@@ -308,7 +308,8 @@ extern "C" {
    @param HeadlossFormula headloss formula flag
    @return error code
    */
-  int  DLLEXPORT ENinit(char *rptFile, char *binOutFile, int UnitsType, int HeadlossFormula);
+  int  DLLEXPORT ENinit(const char *rptFile, const char *binOutFile, 
+    int UnitsType, int HeadlossFormula);
   
   /**
    @brief Opens EPANET input file & reads in network data
@@ -317,14 +318,14 @@ extern "C" {
    @param binOutFile pointer to name of binary output file (to be created)
    @return error code
    */
-  int  DLLEXPORT ENopen(char *inpFile, char *rptFile, char *binOutFile);
+  int  DLLEXPORT ENopen(const char *inpFile, const char *rptFile, const char *binOutFile);
   
   /**
    @brief Saves current data to "INP" formatted text file.
    @param filename The file path to create
    @return Error code
    */
-  int  DLLEXPORT ENsaveinpfile(char *filename);
+  int  DLLEXPORT ENsaveinpfile(const char *filename);
   
   /**
    @brief Frees all memory and files used by EPANET
@@ -1200,13 +1201,13 @@ extern "C" {
 
   //int DLLEXPORT EN_epanet(EN_ProjectHandle ph, const char *f1, const char *f2,
 	//  const char *f3, void(*pviewprog)(char *));
-  int DLLEXPORT EN_init(EN_ProjectHandle ph, char *rptFile, char *binOutFile,
+  int DLLEXPORT EN_init(EN_ProjectHandle ph, const char *rptFile, const char *binOutFile,
           EN_FlowUnits UnitsType, EN_FormType HeadlossFormula);
 
   int DLLEXPORT EN_open(EN_ProjectHandle ph, const char *inpFile,
           const char *rptFile, const char *binOutFile);
 
-  int DLLEXPORT EN_saveinpfile(EN_ProjectHandle ph, char *filename);
+  int DLLEXPORT EN_saveinpfile(EN_ProjectHandle ph, const char *filename);
 
   int DLLEXPORT EN_close(EN_ProjectHandle ph);
   int DLLEXPORT EN_solveH(EN_ProjectHandle ph);
diff --git a/src/epanet.c b/src/epanet.c
index 72bc727..d8e3cc4 100644
--- a/src/epanet.c
+++ b/src/epanet.c
@@ -185,7 +185,7 @@ int DLLEXPORT ENepanet(const char *f1, const char *f2, const char *f3, void (*pv
   return (errcode);
 }
 
-int DLLEXPORT ENinit(char *f2, char *f3, int UnitsType,
+int DLLEXPORT ENinit(const char *f2, const char *f3, int UnitsType,
                      int HeadlossFormula) {
   int errcode = 0;
   ERRCODE(EN_createproject(&_defaultModel));
@@ -193,14 +193,14 @@ int DLLEXPORT ENinit(char *f2, char *f3, int UnitsType,
   return (errcode);
 }
 
-int DLLEXPORT ENopen(char *f1, char *f2, char *f3) {
+int DLLEXPORT ENopen(const char *f1, const char *f2, const char *f3) {
   int errcode = 0;
   ERRCODE(EN_createproject(&_defaultModel));
   EN_open(_defaultModel, f1, f2, f3);
   return (errcode);
 }
 
-int DLLEXPORT ENsaveinpfile(char *filename) {
+int DLLEXPORT ENsaveinpfile(const char *filename) {
   return EN_saveinpfile(_defaultModel, filename);
 }
 
@@ -642,7 +642,7 @@ int DLLEXPORT EN_runproject(EN_ProjectHandle ph, const char *f1, const char *f2,
     return errcode;
 }
 
-int DLLEXPORT EN_init(EN_ProjectHandle ph, char *f2, char *f3,
+int DLLEXPORT EN_init(EN_ProjectHandle ph, const char *f2, const char *f3,
                       EN_FlowUnits UnitsType, EN_FormType HeadlossFormula)
 /*----------------------------------------------------------------
  **  Input:
@@ -777,7 +777,7 @@ int DLLEXPORT EN_open(EN_ProjectHandle ph, const char *f1, const char *f2, const
   return set_error(p->error_handle, errcode);
 }
 
-int DLLEXPORT EN_saveinpfile(EN_ProjectHandle ph, char *filename)
+int DLLEXPORT EN_saveinpfile(EN_ProjectHandle ph, const char *filename)
 /*----------------------------------------------------------------
  **  Input:   filename = name of INP file
  **  Output:  none
diff --git a/src/funcs.h b/src/funcs.h
index b961a82..07d9303 100755
--- a/src/funcs.h
+++ b/src/funcs.h
@@ -248,6 +248,6 @@ int     saveepilog(EN_Project *pr);                 /* Saves output file epilog
 
 
 /* ------------ INPFILE.C --------------*/
-int     saveinpfile(EN_Project *pr, char *);        /* Saves network to text file  */
+int     saveinpfile(EN_Project *pr, const char *);  /* Saves network to text file  */
 
 #endif
diff --git a/src/inpfile.c b/src/inpfile.c
index 9e4b130..1d7c11e 100644
--- a/src/inpfile.c
+++ b/src/inpfile.c
@@ -114,7 +114,7 @@ void saveauxdata(parser_data_t *parser, FILE *f)
 
 ////  This function was heavily modified.  //// 
 
-int saveinpfile(EN_Project *pr, char *fname)
+int saveinpfile(EN_Project *pr, const char *fname)
 /*
 -------------------------------------------------
   Writes network data to text file.
diff --git a/tests/test_net_builder.cpp b/tests/test_net_builder.cpp
index d279664..7721fe8 100644
--- a/tests/test_net_builder.cpp
+++ b/tests/test_net_builder.cpp
@@ -47,7 +47,7 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
     error = EN_open(ph, path_inp.c_str(), path_rpt.c_str(), path_out.c_str());
     BOOST_REQUIRE(error == 0);
 
-    error = EN_getnodeindex(ph, "2", &Nindex);
+    error = EN_getnodeindex(ph, (char *)"2", &Nindex);
     BOOST_REQUIRE(error == 0);
 
     error = EN_openH(ph);
@@ -86,11 +86,11 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
     float Y[9] = {70, 70, 70, 70, 40, 40, 40, 10, 10 };
     float L[12] = {10530, 5280, 5280, 5280, 5280, 5280, 200, 5280, 5280, 5280, 5280, 5280};
     float dia[12] = { 18, 14, 10, 10, 12, 6, 18, 10, 12, 8, 8, 6 };
-    float P[12] = { 1, 1.2, 1.4, 1.6, 1.4, 1.2, 1, 0.8, 0.6, 0.4, 0.6, 0.8 };
+    float P[12] = { 1.0f, 1.2f, 1.4f, 1.6f, 1.4f, 1.2f, 1.0f, 0.8f, 0.6f, 0.4f, 0.6f, 0.8f };
 
     error = EN_createproject(&ph);
     error = EN_init(ph, "net.rpt", "net.out", EN_GPM, EN_HW);
-    error = EN_addpattern(ph, "1");
+    error = EN_addpattern(ph, (char *)"1");
     BOOST_REQUIRE(error == 0);
     error = EN_setpattern(ph, 1, P, 12);
     BOOST_REQUIRE(error == 0);
@@ -107,14 +107,14 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
       error = EN_setdemandpattern(ph, i + 1, 1, 1);
       BOOST_REQUIRE(error == 0);
     }
-    error = EN_addnode(ph, "9", EN_RESERVOIR);
+    error = EN_addnode(ph, (char *)"9", EN_RESERVOIR);
     BOOST_REQUIRE(error == 0);
     error = EN_setcoord(ph, 10, 10, 70);
     BOOST_REQUIRE(error == 0);
     error = EN_setnodevalue(ph, 10, EN_ELEVATION, 800);
     BOOST_REQUIRE(error == 0);
 
-    error = EN_addnode(ph, "2", EN_TANK);
+    error = EN_addnode(ph, (char *)"2", EN_TANK);
     BOOST_REQUIRE(error == 0);
     error = EN_setcoord(ph, 11, 50, 90);
     BOOST_REQUIRE(error == 0);
@@ -131,29 +131,29 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
     error = EN_setnodevalue(ph, 11, EN_MIXFRACTION, 1);
     BOOST_REQUIRE(error == 0);
 
-    error = EN_addlink(ph, "10", EN_PIPE, "10", "11");
+    error = EN_addlink(ph, (char *)"10", EN_PIPE, (char *)"10", (char *)"11");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "11", EN_PIPE, "11", "12");
+    error = EN_addlink(ph, (char *)"11", EN_PIPE, (char *)"11", (char *)"12");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "12", EN_PIPE, "12", "13");
+    error = EN_addlink(ph, (char *)"12", EN_PIPE, (char *)"12", (char *)"13");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "21", EN_PIPE, "21", "22");
+    error = EN_addlink(ph, (char *)"21", EN_PIPE, (char *)"21", (char *)"22");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "22", EN_PIPE, "22", "23");
+    error = EN_addlink(ph, (char *)"22", EN_PIPE, (char *)"22", (char *)"23");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "31", EN_PIPE, "31", "32");
+    error = EN_addlink(ph, (char *)"31", EN_PIPE, (char *)"31", (char *)"32");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "110", EN_PIPE, "2", "12");
+    error = EN_addlink(ph, (char *)"110", EN_PIPE, (char *)"2", (char *)"12");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "111", EN_PIPE, "11", "21");
+    error = EN_addlink(ph, (char *)"111", EN_PIPE, (char *)"11", (char *)"21");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "112", EN_PIPE, "12", "22");
+    error = EN_addlink(ph, (char *)"112", EN_PIPE, (char *)"12", (char *)"22");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "113", EN_PIPE, "13", "23");
+    error = EN_addlink(ph, (char *)"113", EN_PIPE, (char *)"13", (char *)"23");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "121", EN_PIPE, "21", "31");
+    error = EN_addlink(ph, (char *)"121", EN_PIPE, (char *)"21", (char *)"31");
     BOOST_REQUIRE(error == 0);
-    error = EN_addlink(ph, "122", EN_PIPE, "22", "32");
+    error = EN_addlink(ph, (char *)"122", EN_PIPE, (char *)"22", (char *)"32");
     BOOST_REQUIRE(error == 0);
     for (i = 0; i < 12; i++)
     {
@@ -163,13 +163,13 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
       BOOST_REQUIRE(error == 0);
     }
 
-    error = EN_addlink(ph, "9", EN_PUMP, "9", "10");
+    error = EN_addlink(ph, (char *)"9", EN_PUMP, (char *)"9", (char *)"10");
     BOOST_REQUIRE(error == 0);
-    error = EN_addcurve(ph, "1");
+    error = EN_addcurve(ph, (char *)"1");
     BOOST_REQUIRE(error == 0);
     error = EN_setcurvevalue(ph, 1, 1, 1500, 250);
     BOOST_REQUIRE(error == 0);
-    error = EN_getlinkindex(ph, "9", &ind);
+    error = EN_getlinkindex(ph, (char *)"9", &ind);
     BOOST_REQUIRE(error == 0);
     error = EN_setheadcurveindex(ph, ind, 1);
     BOOST_REQUIRE(error == 0);
@@ -179,9 +179,9 @@ BOOST_AUTO_TEST_CASE(test_net_builder)
     error = EN_settimeparam(ph, EN_PATTERNSTEP, 2*3600);
     BOOST_REQUIRE(error == 0);
 
-    error = EN_getlinkindex(ph, "9", &Lindex);
+    error = EN_getlinkindex(ph, (char *)"9", &Lindex);
     BOOST_REQUIRE(error == 0);
-    error = EN_getnodeindex(ph, "2", &Nindex);
+    error = EN_getnodeindex(ph, (char *)"2", &Nindex);
     BOOST_REQUIRE(error == 0);
 
     // Add controls