diff --git a/include/epanet2.h b/include/epanet2.h
index ec32e67..36a1f0f 100644
--- a/include/epanet2.h
+++ b/include/epanet2.h
@@ -75,11 +75,11 @@ extern "C" {
 
   int  DLLEXPORT ENgettitle(char *line1, char *line2, char *line3);
 
-  int  DLLEXPORT ENsettitle(char *line1, char *line2, char *line3);
+  int  DLLEXPORT ENsettitle(const char *line1, const char *line2, const char *line3);
 
   int  DLLEXPORT ENgetcomment(int object, int index, char *comment);
 
-  int  DLLEXPORT ENsetcomment(int object, int index, char *comment);
+  int  DLLEXPORT ENsetcomment(int object, int index, const char *comment);
 
   int  DLLEXPORT ENgetcount(int object, int *count);
 
@@ -107,9 +107,9 @@ extern "C" {
 
   int  DLLEXPORT ENcloseH();
 
-  int  DLLEXPORT ENsavehydfile(char *filename);
+  int  DLLEXPORT ENsavehydfile(const char *filename);
 
-  int  DLLEXPORT ENusehydfile(char *filename);
+  int  DLLEXPORT ENusehydfile(const char *filename);
 
 /********************************************************************
 
@@ -137,17 +137,17 @@ extern "C" {
 
 ********************************************************************/
 
-  int  DLLEXPORT ENwriteline(char *line);
+  int  DLLEXPORT ENwriteline(const char *line);
 
   int  DLLEXPORT ENreport();
 
-  int  DLLEXPORT ENcopyreport(char *filename);
+  int  DLLEXPORT ENcopyreport(const char *filename);
 
   int  DLLEXPORT ENclearreport();
 
   int  DLLEXPORT ENresetreport();
 
-  int  DLLEXPORT ENsetreport(char *format);
+  int  DLLEXPORT ENsetreport(const char *format);
 
   int  DLLEXPORT ENsetstatusreport(int level);
 
@@ -161,7 +161,7 @@ extern "C" {
 
   int  DLLEXPORT ENtimetonextevent(int *eventType, long *duration, int *elementIndex);
 
-  int DLLEXPORT ENsetreportcallback(void (*callback)(void *userData, void *EN_projectHandle, char*));
+  int DLLEXPORT ENsetreportcallback(void (*callback)(void *userData, void *EN_projectHandle, const char*));
   int DLLEXPORT ENsetreportcallbackuserdata(void *userData);
 
 
@@ -188,8 +188,8 @@ extern "C" {
 
   int  DLLEXPORT ENgetqualtype(int *qualType, int *traceNode);
 
-  int  DLLEXPORT ENsetqualtype(int qualType, char *chemName, char *chemUnits,
-                 char *traceNode);
+  int  DLLEXPORT ENsetqualtype(int qualType, const char *chemName,
+                 const char *chemUnits, const char *traceNode);
 
 /********************************************************************
 
@@ -197,15 +197,15 @@ extern "C" {
 
 ********************************************************************/
 
-   int DLLEXPORT ENaddnode(char *id, int nodeType, int *index);
+   int DLLEXPORT ENaddnode(const char *id, int nodeType, int *index);
 
    int DLLEXPORT ENdeletenode(int index, int actionCode);
 
-   int DLLEXPORT ENgetnodeindex(char *id, int *index);
+   int DLLEXPORT ENgetnodeindex(const char *id, int *index);
 
    int DLLEXPORT ENgetnodeid(int index, char *id);
 
-   int DLLEXPORT ENsetnodeid(int index, char *newid);
+   int DLLEXPORT ENsetnodeid(int index, const char *newid);
 
    int DLLEXPORT ENgetnodetype(int index, int *nodeType);
 
@@ -214,12 +214,12 @@ extern "C" {
    int DLLEXPORT ENsetnodevalue(int index, int property, EN_API_FLOAT_TYPE value);
 
    int DLLEXPORT ENsetjuncdata(int index, EN_API_FLOAT_TYPE elev,
-                 EN_API_FLOAT_TYPE dmnd, char *dmndpat);
+                 EN_API_FLOAT_TYPE dmnd, const char *dmndpat);
 
   int  DLLEXPORT ENsettankdata(int index, EN_API_FLOAT_TYPE elev,
                  EN_API_FLOAT_TYPE initlvl, EN_API_FLOAT_TYPE minlvl,
                  EN_API_FLOAT_TYPE maxlvl, EN_API_FLOAT_TYPE diam,
-                 EN_API_FLOAT_TYPE minvol, char *volcurve);
+                 EN_API_FLOAT_TYPE minvol, const char *volcurve);
 
   int  DLLEXPORT ENgetcoord(int index, double *x, double *y);
 
@@ -238,13 +238,14 @@ extern "C" {
                 EN_API_FLOAT_TYPE preq, EN_API_FLOAT_TYPE pexp);
 
   int DLLEXPORT ENadddemand(int nodeIndex, EN_API_FLOAT_TYPE baseDemand,
-                char *demandPattern, char *demandName);
+                const char *demandPattern, const char *demandName);
 
   int DLLEXPORT ENdeletedemand(int nodeIndex, int demandIndex);
 
   int DLLEXPORT ENgetnumdemands(int nodeIndex, int *numDemands);
 
-  int DLLEXPORT ENgetdemandindex(int nodeIndex, char *demandName, int *demandIndex);
+  int DLLEXPORT ENgetdemandindex(int nodeIndex, const char *demandName,
+                int *demandIndex);
 
   int DLLEXPORT ENgetbasedemand(int nodeIndex, int demandIndex,
                 EN_API_FLOAT_TYPE *baseDemand);
@@ -258,7 +259,7 @@ extern "C" {
 
   int DLLEXPORT ENgetdemandname(int nodeIndex, int demandIndex, char *demandName);
 
-  int DLLEXPORT ENsetdemandname(int nodeIndex, int demandIndex, char *demandName);
+  int DLLEXPORT ENsetdemandname(int nodeIndex, int demandIndex, const char *demandName);
 
 /********************************************************************
 
@@ -266,15 +267,16 @@ extern "C" {
 
 ********************************************************************/
 
-  int DLLEXPORT ENaddlink(char *id, int linkType, char *fromNode, char *toNode, int *index);
+  int DLLEXPORT ENaddlink(const char *id, int linkType, const char *fromNode,
+                const char *toNode, int *index);
 
   int DLLEXPORT ENdeletelink(int index, int actionCode);
 
-  int DLLEXPORT ENgetlinkindex(char *id, int *index);
+  int DLLEXPORT ENgetlinkindex(const char *id, int *index);
 
   int DLLEXPORT ENgetlinkid(int index, char *id);
 
-  int DLLEXPORT ENsetlinkid(int index, char *newid);
+  int DLLEXPORT ENsetlinkid(int index, const char *newid);
 
   int DLLEXPORT ENgetlinktype(int index, int *linkType);
 
@@ -318,15 +320,15 @@ extern "C" {
 
 ********************************************************************/
 
-  int DLLEXPORT ENaddpattern(char *id);
+  int DLLEXPORT ENaddpattern(const char *id);
 
   int DLLEXPORT ENdeletepattern(int index);
 
-  int DLLEXPORT ENgetpatternindex(char *id, int *index);
+  int DLLEXPORT ENgetpatternindex(const char *id, int *index);
 
   int DLLEXPORT ENgetpatternid(int index, char *id);
 
-  int DLLEXPORT ENsetpatternid(int index, char *id);
+  int DLLEXPORT ENsetpatternid(int index, const char *id);
 
   int DLLEXPORT ENgetpatternlen(int index, int *len);
 
@@ -344,15 +346,15 @@ extern "C" {
 
 ********************************************************************/
 
-  int DLLEXPORT ENaddcurve(char *id);
+  int DLLEXPORT ENaddcurve(const char *id);
 
   int DLLEXPORT ENdeletecurve(int index);
 
-  int DLLEXPORT ENgetcurveindex(char *id, int *index);
+  int DLLEXPORT ENgetcurveindex(const char *id, int *index);
 
   int DLLEXPORT ENgetcurveid(int index, char *id);
 
-  int DLLEXPORT ENsetcurveid(int index, char *id);
+  int DLLEXPORT ENsetcurveid(int index, const char *id);
 
   int DLLEXPORT ENgetcurvelen(int index, int *len);
 
diff --git a/include/epanet2_2.h b/include/epanet2_2.h
index 76dea18..62e3d1a 100644
--- a/include/epanet2_2.h
+++ b/include/epanet2_2.h
@@ -144,7 +144,8 @@ typedef struct Project *EN_Project;
   @param line3 third title line
   @return an error code
   */
-  int  DLLEXPORT EN_settitle(EN_Project ph, char *line1, char *line2, char *line3);
+  int  DLLEXPORT EN_settitle(EN_Project ph, const char *line1, const char *line2,
+      const char *line3);
 
   /**
   @brief Retrieves a descriptive comment assigned to a Node, Link, Pattern or Curve.
@@ -164,7 +165,8 @@ typedef struct Project *EN_Project;
   @param comment the comment string assigned to the object
   @return an error code
   */
-  int  DLLEXPORT EN_setcomment(EN_Project ph, int object, int index, char *comment);
+  int  DLLEXPORT EN_setcomment(EN_Project ph, int object, int index,
+      const char *comment);
 
   /**
   @brief Retrieves the number of objects of a given type in a project.
@@ -526,7 +528,7 @@ typedef struct Project *EN_Project;
            use the userData parameter to pass any client context necessary (a context pointer or wrapper object perhaps).
            Leave un-set or set the report callback to NULL to revert to EPANET's default behavior.
   **/
-  int DLLEXPORT EN_setreportcallback(EN_Project ph, void (*callback)(void *userData, void *EN_projectHandle, char*));
+  int DLLEXPORT EN_setreportcallback(EN_Project ph, void (*callback)(void *userData, void *EN_projectHandle, const char*));
   int DLLEXPORT EN_setreportcallbackuserdata(EN_Project ph, void *userData);
 
   /**
@@ -535,7 +537,7 @@ typedef struct Project *EN_Project;
   @param line a text string to write.
   @return an error code.
   */
-  int  DLLEXPORT EN_writeline(EN_Project ph, char *line);
+  int  DLLEXPORT EN_writeline(EN_Project ph, const char *line);
 
   /**
   @brief Writes simulation results in a tabular format to a project's report file.
@@ -560,7 +562,7 @@ typedef struct Project *EN_Project;
   This function allows toolkit clients to retrieve the contents of a project's
   report file while the project is still open.
   */
-  int  DLLEXPORT EN_copyreport(EN_Project ph, char *filename);
+  int  DLLEXPORT EN_copyreport(EN_Project ph, const char *filename);
 
   /**
   @brief Clears the contents of a project's report file.
@@ -598,7 +600,7 @@ typedef struct Project *EN_Project;
   Formatted results of a simulation can be written to a project's report file
   using the ::EN_report function.
   */
-  int  DLLEXPORT EN_setreport(EN_Project ph, char *format);
+  int  DLLEXPORT EN_setreport(EN_Project ph, const char *format);
 
   /**
   @brief Sets the level of hydraulic status reporting.
@@ -637,7 +639,7 @@ typedef struct Project *EN_Project;
   @param maxLen maximum number of characters that errmsg can hold
   @return an error code
 
-  Error message strings should be at least @ref EN_SizeLimits "EN_MAXMSG" characters in length.
+  Error message strings should be greater than @ref EN_SizeLimits "EN_MAXMSG" characters in length.
   */
   int  DLLEXPORT EN_geterror(int errcode, char *out_errmsg, int maxLen);
 
@@ -776,8 +778,8 @@ typedef struct Project *EN_Project;
 
   Note that the trace node is specified by ID name and not by index.
   */
-  int  DLLEXPORT EN_setqualtype(EN_Project ph, int qualType, char *chemName,
-                 char *chemUnits, char *traceNode);
+  int  DLLEXPORT EN_setqualtype(EN_Project ph, int qualType, const char *chemName,
+                 const char *chemUnits, const char *traceNode);
 
   /********************************************************************
 
@@ -795,7 +797,7 @@ typedef struct Project *EN_Project;
 
   When a new node is created all of its properties (see @ref EN_NodeProperty) are set to 0.
   */
-  int DLLEXPORT EN_addnode(EN_Project ph, char *id, int nodeType, int *out_index);
+  int DLLEXPORT EN_addnode(EN_Project ph, const char *id, int nodeType, int *out_index);
 
   /**
   @brief Deletes a node from a project.
@@ -819,7 +821,7 @@ typedef struct Project *EN_Project;
   @param[out] index the node's index (starting from 1).
   @return an error code
   */
-  int  DLLEXPORT EN_getnodeindex(EN_Project ph, char *id, int *out_index);
+  int  DLLEXPORT EN_getnodeindex(EN_Project ph, const char *id, int *out_index);
 
   /**
   @brief Gets the ID name of a node given its index.
@@ -828,7 +830,7 @@ typedef struct Project *EN_Project;
   @param[out] out_id the node's ID name.
   @return an error code
 
-  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID" characters.
+  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getnodeid(EN_Project ph, int index, char *out_id);
 
@@ -841,7 +843,7 @@ typedef struct Project *EN_Project;
 
   The ID name must not be longer than @ref EN_SizeLimits "EN_MAXID" characters.
   */
-  int DLLEXPORT EN_setnodeid(EN_Project ph, int index, char *newid);
+  int DLLEXPORT EN_setnodeid(EN_Project ph, int index, const char *newid);
 
   /**
   @brief Retrieves a node's type given its index.
@@ -889,7 +891,7 @@ typedef struct Project *EN_Project;
   These properties have units that depend on the units used for flow rate (see @ref Units).
   */
   int  DLLEXPORT EN_setjuncdata(EN_Project ph, int index, double elev, double dmnd,
-      char *dmndpat);
+      const char *dmndpat);
 
   /**
   @brief Sets a group of properties for a tank node.
@@ -907,7 +909,7 @@ typedef struct Project *EN_Project;
   These properties have units that depend on the units used for flow rate (see @ref Units).
   */
   int  DLLEXPORT EN_settankdata(EN_Project ph, int index, double elev, double initlvl,
-                 double minlvl, double maxlvl, double diam, double minvol, char *volcurve);
+                 double minlvl, double maxlvl, double diam, double minvol, const char *volcurve);
 
   /**
   @brief Gets the (x,y) coordinates of a node.
@@ -985,7 +987,7 @@ typedef struct Project *EN_Project;
   that no time pattern or category name is associated with the demand.
   */
   int DLLEXPORT EN_adddemand(EN_Project ph, int nodeIndex, double baseDemand,
-                char *demandPattern, char *demandName);
+                const char *demandPattern, const char *demandName);
 
   /**
   @brief deletes a demand from a junction node.
@@ -1004,7 +1006,7 @@ typedef struct Project *EN_Project;
   @param[out] demandIndex the index of the demand being sought
   @return an error code
   */
-  int DLLEXPORT EN_getdemandindex(EN_Project ph, int nodeIndex, char *demandName,
+  int DLLEXPORT EN_getdemandindex(EN_Project ph, int nodeIndex, const char *demandName,
                 int *out_demandIndex);
 
   /**
@@ -1073,7 +1075,7 @@ typedef struct Project *EN_Project;
   @param[out] out_demandName The name of the selected category.
   @return an error code.
 
-  \b demandName must be sized to contain at least @ref EN_SizeLimits "EN_MAXID" characters.
+  \b demandName must be sized to contain at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int DLLEXPORT EN_getdemandname(EN_Project ph, int nodeIndex, int demandIndex, char *out_demandName);
 
@@ -1087,7 +1089,8 @@ typedef struct Project *EN_Project;
 
   The category name must contain no more than @ref EN_SizeLimits "EN_MAXID" characters.
   */
-  int DLLEXPORT EN_setdemandname(EN_Project ph, int nodeIndex, int demandIdx, char *demandName);
+  int DLLEXPORT EN_setdemandname(EN_Project ph, int nodeIndex, int demandIdx,
+                const char *demandName);
 
   /********************************************************************
 
@@ -1120,8 +1123,8 @@ typedef struct Project *EN_Project;
 
   See @ref EN_LinkProperty.
   */
-  int DLLEXPORT EN_addlink(EN_Project ph, char *id, int linkType, char *fromNode,
-                          char *toNode, int *out_index);
+  int DLLEXPORT EN_addlink(EN_Project ph, const char *id, int linkType, const char *fromNode,
+                          const char *toNode, int *out_index);
 
   /**
   @brief Deletes a link from the project.
@@ -1143,7 +1146,7 @@ typedef struct Project *EN_Project;
   @param[out] index the link's index (starting from 1).
   @return an error code.
   */
-  int  DLLEXPORT EN_getlinkindex(EN_Project ph, char *id, int *out_index);
+  int  DLLEXPORT EN_getlinkindex(EN_Project ph, const char *id, int *out_index);
 
   /**
   @brief Gets the ID name of a link given its index.
@@ -1152,7 +1155,7 @@ typedef struct Project *EN_Project;
   @param[out] out_id The link's ID name.
   @return an error code.
 
-  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID" characters.
+  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getlinkid(EN_Project ph, int index, char *out_id);
 
@@ -1165,7 +1168,7 @@ typedef struct Project *EN_Project;
 
   The ID name must not be longer than @ref EN_SizeLimits "EN_MAXID" characters.
   */
-  int DLLEXPORT EN_setlinkid(EN_Project ph, int index, char *newid);
+  int DLLEXPORT EN_setlinkid(EN_Project ph, int index, const char *newid);
 
   /**
   @brief Retrieves a link's type.
@@ -1341,7 +1344,7 @@ typedef struct Project *EN_Project;
 
   The new pattern contains a single time period whose factor is 1.0.
   */
-  int  DLLEXPORT EN_addpattern(EN_Project ph, char *id);
+  int  DLLEXPORT EN_addpattern(EN_Project ph, const char *id);
 
   /**
   @brief Deletes a time pattern from a project.
@@ -1358,7 +1361,7 @@ typedef struct Project *EN_Project;
   @param[out] index the time pattern's index (starting from 1).
   @return an error code.
   */
-  int  DLLEXPORT EN_getpatternindex(EN_Project ph, char *id, int *out_index);
+  int  DLLEXPORT EN_getpatternindex(EN_Project ph, const char *id, int *out_index);
 
   /**
   @brief Retrieves the ID name of a time pattern given its index.
@@ -1367,7 +1370,7 @@ typedef struct Project *EN_Project;
   @param[out] out_id the time pattern's ID name.
   @return an error code.
 
-  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID" characters.
+  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getpatternid(EN_Project ph, int index, char *out_id);
 
@@ -1380,7 +1383,7 @@ typedef struct Project *EN_Project;
 
   The new ID name must not exceed @ref EN_SizeLimits "EN_MAXID" characters.
   */
-  int  DLLEXPORT EN_setpatternid(EN_Project ph, int index, char *id);
+  int  DLLEXPORT EN_setpatternid(EN_Project ph, int index, const char *id);
 
   /**
   @brief Retrieves the number of time periods in a time pattern.
@@ -1449,7 +1452,7 @@ typedef struct Project *EN_Project;
 
   The new curve contains a single data point (1.0, 1.0).
   */
-  int  DLLEXPORT EN_addcurve(EN_Project ph, char *id);
+  int  DLLEXPORT EN_addcurve(EN_Project ph, const char *id);
 
   /**
   @brief Deletes a data curve from a project.
@@ -1466,7 +1469,7 @@ typedef struct Project *EN_Project;
   @param[out] index The curve's index (starting from 1).
   @return an error code.
   */
-  int  DLLEXPORT EN_getcurveindex(EN_Project ph, char *id, int *out_index);
+  int  DLLEXPORT EN_getcurveindex(EN_Project ph, const char *id, int *out_index);
 
   /**
   @brief Retrieves the ID name of a curve given its index.
@@ -1475,7 +1478,7 @@ typedef struct Project *EN_Project;
   @param[out] out_id the curve's ID name.
   @return an error code.
 
-  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID" characters.
+  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getcurveid(EN_Project ph, int index, char *out_id);
 
@@ -1488,7 +1491,7 @@ typedef struct Project *EN_Project;
 
   The new ID name must not exceed @ref EN_SizeLimits "EN_MAXID" characters.
   */
-  int  DLLEXPORT EN_setcurveid(EN_Project ph, int index, char *id);
+  int  DLLEXPORT EN_setcurveid(EN_Project ph, int index, const char *id);
 
   /**
   @brief Retrieves the number of points in a curve.
@@ -1553,7 +1556,7 @@ typedef struct Project *EN_Project;
 
   The calling program is responsible for making `xValues` and `yValues` large enough
   to hold `nPoints` number of data points and for sizing `id` to hold at least
-  @ref EN_SizeLimits "EN_MAXID" characters.
+  @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getcurve(EN_Project ph, int index, char *out_id, int *out_nPoints,
                  double *out_xValues, double *out_yValues);
@@ -1683,7 +1686,7 @@ typedef struct Project *EN_Project;
   @param[out] out_id the rule's ID name.
   @return Error code.
 
-  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID" characters.
+  The ID name must be sized to hold at least @ref EN_SizeLimits "EN_MAXID+1" characters.
   */
   int  DLLEXPORT EN_getruleID(EN_Project ph, int index, char *out_id);
 
diff --git a/src/epanet.c b/src/epanet.c
index 6516f7a..d9e0280 100644
--- a/src/epanet.c
+++ b/src/epanet.c
@@ -251,7 +251,8 @@ int DLLEXPORT EN_gettitle(EN_Project p, char *line1, char *line2, char *line3)
     return 0;
 }
 
-int DLLEXPORT EN_settitle(EN_Project p, char *line1, char *line2, char *line3)
+int DLLEXPORT EN_settitle(EN_Project p, const char *line1, 
+    const char *line2, const char *line3)
 /*----------------------------------------------------------------
 **  Input:  line1, line2, line3 = project's title lines
 **  Returns: error code
@@ -279,7 +280,8 @@ int DLLEXPORT EN_getcomment(EN_Project p, int object, int index, char *comment)
     return getcomment(&p->network, object, index, comment);
 }
 
-int  DLLEXPORT EN_setcomment(EN_Project p, int object, int index, char *comment)
+int  DLLEXPORT EN_setcomment(EN_Project p, int object, int index,
+    const char *comment)
 /*----------------------------------------------------------------
 **  Input:   object = a type of object (see EN_ObjectType)
 **           index = the object's index
@@ -842,7 +844,7 @@ int DLLEXPORT EN_closeQ(EN_Project p)
  ********************************************************************/
 
 
- int  DLLEXPORT EN_setreportcallback(EN_Project p, void (*callback)(void*,void*,char*))
+ int  DLLEXPORT EN_setreportcallback(EN_Project p, void (*callback)(void*,void*,const char*))
  {
    p->report.reportCallback = callback;
    return 0;
@@ -854,7 +856,7 @@ int DLLEXPORT EN_closeQ(EN_Project p)
    return 0;
  }
 
-int DLLEXPORT EN_writeline(EN_Project p, char *line)
+int DLLEXPORT EN_writeline(EN_Project p, const char *line)
 /*----------------------------------------------------------------
 **  Input:   line = line of text
 **  Output:  none
@@ -890,7 +892,7 @@ int DLLEXPORT EN_report(EN_Project p)
     return errcode;
 }
 
-int  DLLEXPORT EN_copyreport(EN_Project p, char *filename)
+int  DLLEXPORT EN_copyreport(EN_Project p, const char *filename)
 /*----------------------------------------------------------------
 **  Input:   filename = name of file to receive copy of report
 **  Output:  none
@@ -939,7 +941,7 @@ int DLLEXPORT EN_resetreport(EN_Project p)
     return 0;
 }
 
-int DLLEXPORT EN_setreport(EN_Project p, char *format)
+int DLLEXPORT EN_setreport(EN_Project p, const char *format)
 /*----------------------------------------------------------------
 **  Input:   format = a report formatting command
 **  Output:  none
@@ -1714,8 +1716,8 @@ int DLLEXPORT EN_getqualtype(EN_Project p, int *qualType, int *traceNode)
     return 0;
 }
 
-int DLLEXPORT EN_setqualtype(EN_Project p, int qualType, char *chemName,
-                             char *chemUnits, char *traceNode)
+int DLLEXPORT EN_setqualtype(EN_Project p, int qualType, const char *chemName,
+                             const char *chemUnits, const char *traceNode)
 /*----------------------------------------------------------------
 **  Input:   qualType = type of quality analysis to run (see EN_QualityType)
 **           chemname = name of chemical constituent
@@ -1794,7 +1796,7 @@ int DLLEXPORT EN_setqualtype(EN_Project p, int qualType, char *chemName,
 
 ********************************************************************/
 
-int DLLEXPORT EN_addnode(EN_Project p, char *id, int nodeType, int *index)
+int DLLEXPORT EN_addnode(EN_Project p, const char *id, int nodeType, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = node ID name
 **           nodeType = type of node (see EN_NodeType)
@@ -2043,7 +2045,7 @@ int DLLEXPORT EN_deletenode(EN_Project p, int index, int actionCode)
     return 0;
 }
 
-int DLLEXPORT EN_getnodeindex(EN_Project p, char *id, int *index)
+int DLLEXPORT EN_getnodeindex(EN_Project p, const char *id, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = node ID name
 **  Output:  index = node index
@@ -2075,7 +2077,7 @@ int DLLEXPORT EN_getnodeid(EN_Project p, int index, char *id)
     return 0;
 }
 
-int DLLEXPORT EN_setnodeid(EN_Project p, int index, char *newid)
+int DLLEXPORT EN_setnodeid(EN_Project p, int index, const char *newid)
 /*----------------------------------------------------------------
 **  Input:   index = node index
 **           newid = new node ID name
@@ -2618,7 +2620,7 @@ int DLLEXPORT EN_setnodevalue(EN_Project p, int index, int property, double valu
 }
 
 int DLLEXPORT EN_setjuncdata(EN_Project p, int index, double elev,
-                             double dmnd, char *dmndpat)
+                             double dmnd, const char *dmndpat)
 /*----------------------------------------------------------------
 **  Input:   index = junction node index
 **           elev = junction elevation
@@ -2663,7 +2665,7 @@ int DLLEXPORT EN_setjuncdata(EN_Project p, int index, double elev,
 int DLLEXPORT EN_settankdata(EN_Project p, int index, double elev,
                              double initlvl, double minlvl,
                              double maxlvl, double diam,
-                             double minvol, char *volcurve)
+                             double minvol, const char *volcurve)
 /*----------------------------------------------------------------
 **  Input:   index = tank node index
 **           elev = tank bottom elevation
@@ -2839,7 +2841,7 @@ int DLLEXPORT EN_setdemandmodel(EN_Project p, int model, double pmin,
 }
 
 int  DLLEXPORT EN_adddemand(EN_Project p, int nodeIndex, double baseDemand,
-                            char *demandPattern, char *demandName)
+                            const char *demandPattern, const char *demandName)
 /*----------------------------------------------------------------
 **  Input:   nodeIndex = node index
 **           baseDemand = baseline demand value
@@ -2926,7 +2928,7 @@ int DLLEXPORT EN_deletedemand(EN_Project p, int nodeIndex, int demandIndex)
     return 0;
 }
 
-int DLLEXPORT EN_getdemandindex(EN_Project p, int nodeIndex, char *demandName,
+int DLLEXPORT EN_getdemandindex(EN_Project p, int nodeIndex, const char *demandName,
                                 int *demandIndex)
 /*----------------------------------------------------------------
 **  Input:   nodeIndex = node index
@@ -3075,7 +3077,7 @@ int DLLEXPORT EN_getdemandname(EN_Project p, int nodeIndex, int demandIndex,
 }
 
 int DLLEXPORT EN_setdemandname(EN_Project p, int nodeIndex, int demandIndex,
-                               char *demandName)
+                               const char *demandName)
 /*----------------------------------------------------------------
 **  Input:   nodeIndex = node index
 **           demandIndex = demand category index
@@ -3165,8 +3167,8 @@ int  DLLEXPORT EN_setdemandpattern(EN_Project p, int nodeIndex, int demandIndex,
 
 ********************************************************************/
 
-int DLLEXPORT EN_addlink(EN_Project p, char *id, int linkType,
-                         char *fromNode, char *toNode, int *index)
+int DLLEXPORT EN_addlink(EN_Project p, const char *id, int linkType,
+                         const char *fromNode, const char *toNode, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = link ID name
 **           type = link type (see EN_LinkType)
@@ -3416,7 +3418,7 @@ int DLLEXPORT EN_deletelink(EN_Project p, int index, int actionCode)
     return 0;
 }
 
-int DLLEXPORT EN_getlinkindex(EN_Project p, char *id, int *index)
+int DLLEXPORT EN_getlinkindex(EN_Project p, const char *id, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = link ID name
 **  Output:  index = link index
@@ -3448,7 +3450,7 @@ int DLLEXPORT EN_getlinkid(EN_Project p, int index, char *id)
     return 0;
 }
 
-int DLLEXPORT EN_setlinkid(EN_Project p, int index, char *newid)
+int DLLEXPORT EN_setlinkid(EN_Project p, int index, const char *newid)
 /*----------------------------------------------------------------
 **  Input:   index = link index
 **           id = link ID name
@@ -4376,7 +4378,7 @@ int DLLEXPORT EN_setheadcurveindex(EN_Project p, int linkIndex, int curveIndex)
 
 ********************************************************************/
 
-int DLLEXPORT EN_addpattern(EN_Project p, char *id)
+int DLLEXPORT EN_addpattern(EN_Project p, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = time pattern ID name
 **  Output:  none
@@ -4468,7 +4470,7 @@ int  DLLEXPORT EN_deletepattern(EN_Project p, int index)
     return 0;
 }
 
-int DLLEXPORT EN_getpatternindex(EN_Project p, char *id, int *index)
+int DLLEXPORT EN_getpatternindex(EN_Project p, const char *id, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = time pattern name
 **  Output:  index = time pattern index
@@ -4509,7 +4511,7 @@ int DLLEXPORT EN_getpatternid(EN_Project p, int index, char *id)
     return 0;
 }
 
-int DLLEXPORT EN_setpatternid(EN_Project p, int index, char *id)
+int DLLEXPORT EN_setpatternid(EN_Project p, int index, const char *id)
 /*----------------------------------------------------------------
 **  Input:   index = time pattern index
 **           id = time pattern ID name
@@ -4653,7 +4655,7 @@ int DLLEXPORT EN_setpattern(EN_Project p, int index, double *values, int len)
 
 ********************************************************************/
 
-int DLLEXPORT EN_addcurve(EN_Project p, char *id)
+int DLLEXPORT EN_addcurve(EN_Project p, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = data curve ID name
 **  Output:  none
@@ -4745,7 +4747,7 @@ int  DLLEXPORT EN_deletecurve(EN_Project p, int index)
     return 0;
 }
 
-int DLLEXPORT EN_getcurveindex(EN_Project p, char *id, int *index)
+int DLLEXPORT EN_getcurveindex(EN_Project p, const char *id, int *index)
 /*----------------------------------------------------------------
 **  Input:   id = data curve name
 **  Output:  index = data curve index
@@ -4777,7 +4779,7 @@ int DLLEXPORT EN_getcurveid(EN_Project p, int index, char *id)
     return 0;
 }
 
-int DLLEXPORT EN_setcurveid(EN_Project p, int index, char *id)
+int DLLEXPORT EN_setcurveid(EN_Project p, int index, const char *id)
 /*----------------------------------------------------------------
 **  Input:   index = data curve index
 **           id = data curve ID name
diff --git a/src/epanet2.c b/src/epanet2.c
index be16f6a..53d1732 100644
--- a/src/epanet2.c
+++ b/src/epanet2.c
@@ -104,7 +104,7 @@ int DLLEXPORT ENgettitle(char *line1, char *line2, char *line3)
     return EN_gettitle(_defaultProject, line1, line2, line3) ;
 }
 
-int DLLEXPORT ENsettitle(char *line1, char *line2, char *line3)
+int DLLEXPORT ENsettitle(const char *line1, const char *line2, const char *line3)
 {
     return EN_settitle(_defaultProject, line1, line2, line3) ;
 }
@@ -114,7 +114,7 @@ int DLLEXPORT ENgetcomment(int object, int index, char *comment)
     return EN_getcomment(_defaultProject, object, index, comment);
 }
 
-int  DLLEXPORT ENsetcomment(int object, int index, char *comment)
+int  DLLEXPORT ENsetcomment(int object, int index, const char *comment)
 {
     return EN_setcomment(_defaultProject, object, index, comment);
 }
@@ -156,12 +156,12 @@ int DLLEXPORT ENnextH(long *tStep) { return EN_nextH(_defaultProject, tStep); }
 
 int DLLEXPORT ENcloseH() { return EN_closeH(_defaultProject); }
 
-int DLLEXPORT ENsavehydfile(char *filename)
+int DLLEXPORT ENsavehydfile(const char *filename)
 {
     return EN_savehydfile(_defaultProject, filename);
 }
 
-int DLLEXPORT ENusehydfile(char *filename)
+int DLLEXPORT ENusehydfile(const char *filename)
 {
     return EN_usehydfile(_defaultProject, filename);
 }
@@ -192,11 +192,11 @@ int DLLEXPORT ENcloseQ() { return EN_closeQ(_defaultProject); }
 
 ********************************************************************/
 
-int DLLEXPORT ENwriteline(char *line) { return EN_writeline(_defaultProject, line); }
+int DLLEXPORT ENwriteline(const char *line) { return EN_writeline(_defaultProject, line); }
 
 int DLLEXPORT ENreport() { return EN_report(_defaultProject); }
 
-int DLLEXPORT ENcopyreport(char *filename)
+int DLLEXPORT ENcopyreport(const char *filename)
 {
     return EN_copyreport(_defaultProject, filename);
 }
@@ -205,14 +205,14 @@ int DLLEXPORT ENclearreport() { return EN_clearreport(_defaultProject); }
 
 int DLLEXPORT ENresetreport() { return EN_resetreport(_defaultProject); }
 
-int DLLEXPORT ENsetreport(char *format) { return EN_setreport(_defaultProject, format); }
+int DLLEXPORT ENsetreport(const char *format) { return EN_setreport(_defaultProject, format); }
 
 int DLLEXPORT ENsetstatusreport(int level)
 {
     return EN_setstatusreport(_defaultProject, level);
 }
 
-int DLLEXPORT ENsetreportcallback(void (*callback)(void *userData, void *EN_projectHandle, char*))
+int DLLEXPORT ENsetreportcallback(void (*callback)(void *userData, void *EN_projectHandle, const char*))
 {
   return EN_setreportcallback(_defaultProject, callback);
 }
@@ -297,8 +297,8 @@ int DLLEXPORT ENgetqualtype(int *qualType, int *traceNode)
     return EN_getqualtype(_defaultProject, qualType, traceNode);
 }
 
-int DLLEXPORT ENsetqualtype(int qualType, char *chemName, char *chemUnits,
-              char *traceNode)
+int DLLEXPORT ENsetqualtype(int qualType, const char *chemName,
+              const char *chemUnits, const char *traceNode)
 {
     return EN_setqualtype(_defaultProject, qualType, chemName, chemUnits, traceNode);
 }
@@ -309,7 +309,7 @@ int DLLEXPORT ENsetqualtype(int qualType, char *chemName, char *chemUnits,
 
 ********************************************************************/
 
-int DLLEXPORT ENaddnode(char *id, int nodeType, int *index)
+int DLLEXPORT ENaddnode(const char *id, int nodeType, int *index)
 {
     return EN_addnode(_defaultProject, id, nodeType, index);
 }
@@ -319,7 +319,7 @@ int DLLEXPORT ENdeletenode(int index, int actionCode)
     return EN_deletenode(_defaultProject, index, actionCode);
 }
 
-int DLLEXPORT ENgetnodeindex(char *id, int *index)
+int DLLEXPORT ENgetnodeindex(const char *id, int *index)
 {
     return EN_getnodeindex(_defaultProject, id, index);
 }
@@ -329,7 +329,7 @@ int DLLEXPORT ENgetnodeid(int index, char *id)
     return EN_getnodeid(_defaultProject, index, id);
 }
 
-int DLLEXPORT ENsetnodeid(int index, char *newid)
+int DLLEXPORT ENsetnodeid(int index, const char *newid)
 {
     return EN_setnodeid(_defaultProject, index, newid);
 }
@@ -353,7 +353,7 @@ int DLLEXPORT ENsetnodevalue(int index, int property, EN_API_FLOAT_TYPE value)
 }
 
 int DLLEXPORT ENsetjuncdata(int index, EN_API_FLOAT_TYPE elev, EN_API_FLOAT_TYPE dmnd,
-              char *dmndpat)
+              const char *dmndpat)
 {
     return EN_setjuncdata(_defaultProject, index, elev, dmnd, dmndpat);
 }
@@ -361,7 +361,7 @@ int DLLEXPORT ENsetjuncdata(int index, EN_API_FLOAT_TYPE elev, EN_API_FLOAT_TYPE
 int  DLLEXPORT ENsettankdata(int index, EN_API_FLOAT_TYPE elev,
                EN_API_FLOAT_TYPE initlvl, EN_API_FLOAT_TYPE minlvl,
                EN_API_FLOAT_TYPE maxlvl, EN_API_FLOAT_TYPE diam,
-               EN_API_FLOAT_TYPE minvol, char *volcurve)
+               EN_API_FLOAT_TYPE minvol, const char *volcurve)
 {
     return EN_settankdata(_defaultProject, index, elev, initlvl, minlvl, maxlvl,
                           diam, minvol, volcurve);
@@ -401,7 +401,7 @@ int DLLEXPORT ENsetdemandmodel(int model, EN_API_FLOAT_TYPE pmin,
 }
 
 int DLLEXPORT ENadddemand(int nodeIndex, EN_API_FLOAT_TYPE baseDemand,
-    char *demandPattern, char *demandName)
+              const char *demandPattern, const char *demandName)
 {
     return EN_adddemand(_defaultProject, nodeIndex, baseDemand, demandPattern, demandName);
 }
@@ -411,7 +411,7 @@ int DLLEXPORT ENdeletedemand(int nodeIndex, int demandIndex)
     return EN_deletedemand(_defaultProject, nodeIndex, demandIndex);
 }
 
-int DLLEXPORT ENgetdemandindex(int nodeIndex, char *demandName, int *demandIndex)
+int DLLEXPORT ENgetdemandindex(int nodeIndex, const char *demandName, int *demandIndex)
 {
     return EN_getdemandindex(_defaultProject, nodeIndex, demandName, demandIndex);
 }
@@ -451,7 +451,7 @@ int DLLEXPORT ENgetdemandname(int nodeIndex, int demandIndex, char *demandName)
     return EN_getdemandname(_defaultProject, nodeIndex, demandIndex, demandName);
 }
 
-int DLLEXPORT ENsetdemandname(int nodeIndex, int demandIndex, char *demandName)
+int DLLEXPORT ENsetdemandname(int nodeIndex, int demandIndex, const char *demandName)
 {
     return EN_setdemandname(_defaultProject, nodeIndex, demandIndex, demandName);
 }
@@ -462,7 +462,8 @@ int DLLEXPORT ENsetdemandname(int nodeIndex, int demandIndex, char *demandName)
 
 ********************************************************************/
 
-int DLLEXPORT ENaddlink(char *id, int linkType, char *fromNode, char *toNode, int *index)
+int DLLEXPORT ENaddlink(const char *id, int linkType, const char *fromNode,
+              const char *toNode, int *index)
 {
     return EN_addlink(_defaultProject, id, linkType, fromNode, toNode, index);
 }
@@ -472,7 +473,7 @@ int DLLEXPORT ENdeletelink(int index, int actionCode)
     return EN_deletelink(_defaultProject, index, actionCode);
 }
 
-int DLLEXPORT ENgetlinkindex(char *id, int *index)
+int DLLEXPORT ENgetlinkindex(const char *id, int *index)
 {
     return EN_getlinkindex(_defaultProject, id, index);
 }
@@ -482,7 +483,7 @@ int DLLEXPORT ENgetlinkid(int index, char *id)
     return EN_getlinkid(_defaultProject, index, id);
 }
 
-int DLLEXPORT ENsetlinkid(int index, char *newid)
+int DLLEXPORT ENsetlinkid(int index, const char *newid)
 {
     return EN_setlinkid(_defaultProject, index, newid);
 }
@@ -573,7 +574,7 @@ int DLLEXPORT ENsetheadcurveindex(int linkIndex, int curveIndex)
 
 ********************************************************************/
 
-int DLLEXPORT ENaddpattern(char *id)
+int DLLEXPORT ENaddpattern(const char *id)
 {
     return EN_addpattern(_defaultProject, id);
 }
@@ -583,7 +584,7 @@ int DLLEXPORT ENdeletepattern(int index)
     return EN_deletepattern(_defaultProject, index);
 }
 
-int DLLEXPORT ENgetpatternindex(char *id, int *index)
+int DLLEXPORT ENgetpatternindex(const char *id, int *index)
 {
     return EN_getpatternindex(_defaultProject, id, index);
 }
@@ -593,7 +594,7 @@ int DLLEXPORT ENgetpatternid(int index, char *id)
     return EN_getpatternid(_defaultProject, index, id);
 }
 
-int DLLEXPORT ENsetpatternid(int index, char *id)
+int DLLEXPORT ENsetpatternid(int index, const char *id)
 {
     return EN_setpatternid(_defaultProject, index, id);
 }
@@ -646,7 +647,7 @@ int DLLEXPORT ENsetpattern(int index, EN_API_FLOAT_TYPE *values, int len)
 
 ********************************************************************/
 
-int DLLEXPORT ENaddcurve(char *id)
+int DLLEXPORT ENaddcurve(const char *id)
 {
     return EN_addcurve(_defaultProject, id);
 }
@@ -656,7 +657,7 @@ int DLLEXPORT ENdeletecurve(int index)
     return EN_deletecurve(_defaultProject, index);
 }
 
-int DLLEXPORT ENgetcurveindex(char *id, int *index)
+int DLLEXPORT ENgetcurveindex(const char *id, int *index)
 {
     return EN_getcurveindex(_defaultProject, id, index);
 }
@@ -666,7 +667,7 @@ int DLLEXPORT ENgetcurveid(int index, char *id)
     return EN_getcurveid(_defaultProject, index, id);
 }
 
-int DLLEXPORT ENsetcurveid(int index, char *id)
+int DLLEXPORT ENsetcurveid(int index, const char *id)
 {
     return EN_setcurveid(_defaultProject, index, id);
 }
diff --git a/src/funcs.h b/src/funcs.h
index 69d3f81..2391477 100755
--- a/src/funcs.h
+++ b/src/funcs.h
@@ -31,16 +31,16 @@ int     incontrols(Project *, int, int);
 int     valvecheck(Project *, int, int, int, int);
 int     unlinked(Project *);
 
-int     findnode(Network *, char *);
-int     findlink(Network *, char *);
+int     findnode(Network *, const char *);
+int     findlink(Network *, const char *);
 int     findtank(Network *, int);
 int     findvalve(Network *, int);
 int     findpump(Network *, int);
-int     findpattern(Network *, char *);
-int     findcurve(Network *, char *);
+int     findpattern(Network *, const char *);
+int     findcurve(Network *, const char *);
 
 Pdemand finddemand(Pdemand, int);
-int     adddemand(Snode *, double, int, char *);
+int     adddemand(Snode *, double, int, const char *);
 void    freedemands(Snode *);
 
 int     addlinkvertex(Slink *, double, double);
@@ -128,13 +128,13 @@ int     checkrules(Project *, long);
 // ------- REPORT.C -----------------
 
 int     clearreport(Project *);
-int     copyreport(Project *, char *);
+int     copyreport(Project *, const char *);
 int     writereport(Project *);
 void    writelogo(Project *);
 void    writesummary(Project *);
 void    writehydstat(Project *, int, double);
 void    writeheader(Project *, int,int);
-void    writeline(Project *, char *);
+void    writeline(Project *, const char *);
 void    writerelerr(Project *, int, double);
 void    writestatchange(Project *, int,char,char);
 void    writecontrolaction(Project *, int, int);
diff --git a/src/hash.c b/src/hash.c
index 4e0099b..411c8ed 100755
--- a/src/hash.c
+++ b/src/hash.c
@@ -26,7 +26,7 @@ typedef struct DataEntryStruct
 } DataEntry;
 
 // Hash a string to an integer
-unsigned int gethash(char *str)
+unsigned int gethash(const char *str)
 {
     unsigned int hash = 5381;
     unsigned int retHash;
@@ -61,7 +61,7 @@ HashTable *hashtable_create()
 }
 
 // Insert an entry into the hash table
-int hashtable_insert(HashTable *ht, char *key, int data)
+int hashtable_insert(HashTable *ht, const char *key, int data)
 {
     unsigned int i = gethash(key);
     DataEntry *entry;
@@ -76,7 +76,7 @@ int hashtable_insert(HashTable *ht, char *key, int data)
 }
 
 // Change the hash table's data entry for a particular key
-int hashtable_update(HashTable *ht, char *key, int new_data)
+int hashtable_update(HashTable *ht, const char *key, int new_data)
 {
     unsigned int i = gethash(key);
     DataEntry *entry;
@@ -96,7 +96,7 @@ int hashtable_update(HashTable *ht, char *key, int new_data)
 }
 
 // Delete an entry in the hash table
-int hashtable_delete(HashTable *ht, char *key)
+int hashtable_delete(HashTable *ht, const char *key)
 {
     unsigned int i = gethash(key);
     DataEntry *entry, *preventry;
@@ -122,7 +122,7 @@ int hashtable_delete(HashTable *ht, char *key)
 }
 
 // Find the data for a particular key
-int hashtable_find(HashTable *ht, char *key)
+int hashtable_find(HashTable *ht, const char *key)
 {
     unsigned int i = gethash(key);
     DataEntry *entry;
@@ -141,7 +141,7 @@ int hashtable_find(HashTable *ht, char *key)
 }
 
 // Find a particular key in the hash table
-char *hashtable_findkey(HashTable *ht, char *key)
+char *hashtable_findkey(HashTable *ht, const char *key)
 {
     unsigned int i = gethash(key);
     DataEntry *entry;
diff --git a/src/hash.h b/src/hash.h
index c847e00..feec4d0 100755
--- a/src/hash.h
+++ b/src/hash.h
@@ -18,11 +18,11 @@
 typedef struct DataEntryStruct *HashTable;
 
 HashTable *hashtable_create(void);
-int       hashtable_insert(HashTable *, char *, int);
-int       hashtable_find(HashTable *, char *);
-char      *hashtable_findkey(HashTable *, char *);
+int       hashtable_insert(HashTable *, const char *, int);
+int       hashtable_find(HashTable *, const char *);
+char      *hashtable_findkey(HashTable *, const char *);
 void      hashtable_free(HashTable *);
-int       hashtable_update(HashTable *ht, char *key, int new_data);
-int       hashtable_delete(HashTable *ht, char *key);
+int       hashtable_update(HashTable *ht, const char *key, int new_data);
+int       hashtable_delete(HashTable *ht, const char *key);
 
 #endif
diff --git a/src/project.c b/src/project.c
index 2aefa21..d5eee6c 100644
--- a/src/project.c
+++ b/src/project.c
@@ -492,7 +492,7 @@ Pdemand finddemand(Pdemand d, int index)
     return d;
 }
 
-int adddemand(Snode *node, double dbase, int dpat, char *dname)
+int adddemand(Snode *node, double dbase, int dpat, const char *dname)
 /*----------------------------------------------------------------
 **  Input:   node = a network junction node
 **           dbase = base demand value
@@ -834,7 +834,7 @@ int unlinked(Project *pr)
     return 0;
 }    
 
-int findnode(Network *network, char *id)
+int findnode(Network *network, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = node ID
 **  Output:  none
@@ -846,7 +846,7 @@ int findnode(Network *network, char *id)
     return (hashtable_find(network->NodeHashTable, id));
 }
 
-int findlink(Network *network, char *id)
+int findlink(Network *network, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = link ID
 **  Output:  none
@@ -909,7 +909,7 @@ int findvalve(Network *network, int index)
     return NOTFOUND;
 }
 
-int findpattern(Network *network, char *id)
+int findpattern(Network *network, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = time pattern ID
 **  Output:  none
@@ -928,7 +928,7 @@ int findpattern(Network *network, char *id)
     return -1;
 }
 
-int findcurve(Network *network, char *id)
+int findcurve(Network *network, const char *id)
 /*----------------------------------------------------------------
 **  Input:   id = data curve ID
 **  Output:  none
diff --git a/src/report.c b/src/report.c
index ae675da..14f55cf 100644
--- a/src/report.c
+++ b/src/report.c
@@ -67,7 +67,7 @@ int clearreport(Project *pr)
     return 0;
 }
 
-int copyreport(Project* pr, char *filename)
+int copyreport(Project* pr, const char *filename)
 /*
 **------------------------------------------------------
 **   Input:   filename = name of file to copy to
@@ -876,7 +876,7 @@ void writeheader(Project *pr, int type, int contin)
     }
 }
 
-void writeline(Project *pr, char *s)
+void writeline(Project *pr, const char *s)
 /*
 **--------------------------------------------------------------
 **   Input:   *s = text string
diff --git a/src/types.h b/src/types.h
index e719c6b..02634e7 100755
--- a/src/types.h
+++ b/src/types.h
@@ -634,7 +634,7 @@ typedef struct {
 
     SField   Field[MAXVAR];  // Output reporting fields
 
-    void (*reportCallback)(void*,void*,char*); // user-supplied reporting callback
+    void (*reportCallback)(void*,void*,const char*); // user-supplied reporting callback
     void *reportCallbackUserData;  // user-supplied reporting context
 
 } Report;