-static char *SwS = {"SWAP:"}; /**< For output that comes from the swap module */
-static char *SwSEmpty = {" "}; /**< Placeholder for multi-line output */
-static char* IonString[eIonNR] = {"anion", "cation" }; /**< Type of ion, used for verbose output */
-static char* IonStr[eIonNR] = {"-", "+" }; /**< Type of ion, used for short output */
-static char* CompStr[eCompNR] = {"A", "B" }; /**< Compartment name */
-static char *SwapStr[eSwapTypesNR+1] = { "", "X-", "Y-", "Z-", NULL}; /**< Name for the swap types. */
-static char *DimStr[DIM+1] = { "X", "Y", "Z", NULL}; /**< Name for the swap dimension. */
+static const char *SwS = {"SWAP:"}; /**< For output that comes from the swap module */
+static const char *SwSEmpty = {" "}; /**< Placeholder for multi-line output */
+static const char* IonString[eIonNR] = {"anion", "cation" }; /**< Type of ion, used for verbose output */
+static const char* IonStr[eIonNR] = {"-", "+" }; /**< Type of ion, used for short output */
+static const char* CompStr[eCompNR] = {"A", "B" }; /**< Compartment name */
+static const char *SwapStr[eSwapTypesNR+1] = { "", "X-", "Y-", "Z-", NULL}; /**< Name for the swap types. */
+static const char *DimStr[DIM+1] = { "X", "Y", "Z", NULL}; /**< Name for the swap dimension. */