diff --git a/CMakeLists.txt b/CMakeLists.txt
new file mode 100644
index 0000000..2c1d6f0
--- /dev/null
+++ b/CMakeLists.txt
@@ -0,0 +1,24 @@
+cmake_minimum_required(VERSION 3.12...3.27)
+
+project(gnuplot_i
+  DESCRIPTION "A gnuplot interface library written in C."
+  LANGUAGES C
+)
+
+# This project is an OBJECT-library, used by other git submodules and the main project.
+add_library(gnuplot_i_ObjLib OBJECT)
+
+# The list of source files.
+target_sources(gnuplot_i_ObjLib
+  PRIVATE
+    "gnuplot_i.c"
+    "gnuplot_i.h"
+)
+
+target_include_directories(gnuplot_i_ObjLib
+  INTERFACE
+    "${CMAKE_CURRENT_SOURCE_DIR}"
+)
+
+# Create an ALIAS target.
+add_library(gnuplot_i::gnuplot_i ALIAS gnuplot_i_ObjLib)
diff --git a/examples/example.c b/examples/example.c
index c3db5be..a215c08 100644
--- a/examples/example.c
+++ b/examples/example.c
@@ -174,7 +174,7 @@ int main(int argc, char *argv[]) {
   h3 = gnuplot_init();
   gnuplot_setstyle(h3, "filledcurves");
   printf("window 1: x*sin(x)\n");
-  gnuplot_cmd(h1, "set linecolor rgb 'blue'");   // this does not work yet
+  gnuplot_cmd(h1, "set style line 1 lc rgb 'blue'");    // Still not working, but doesn't print an error anymore.
   gnuplot_plot_equation(h1, "x*sin(x)", "x*sin(x)");
   sleep(SECONDS);
   printf("window 2: log(x)/x\n");
diff --git a/gnuplot_i.c b/gnuplot_i.c
old mode 100755
new mode 100644
index e8ecd0e..ae175c5
--- a/gnuplot_i.c
+++ b/gnuplot_i.c
@@ -79,7 +79,7 @@
  */
 /*-------------------------------------------------------------------------*/
 
-int mkstemp (char *name) {
+int mkstemp (char const* name) {
   srand(time(NULL));
   int i;
   char *start = strstr(name, "XXXXXX");
@@ -125,9 +125,9 @@ int mkstemp (char *name) {
  */
 /*-------------------------------------------------------------------------*/
 
-char *gnuplot_get_program_path (char *pname) {
+char const* gnuplot_get_program_path (char const* pname) {
   int i, j, lg;
-  char *path;
+  char const* path;
   static char buf[PATH_MAXNAMESZ];
 
   /* Trivial case: try in current working directory */
@@ -297,7 +297,7 @@ void gnuplot_close (gnuplot_ctrl *handle) {
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_cmd (gnuplot_ctrl *handle, char *cmd, ...) {
+void gnuplot_cmd (gnuplot_ctrl *handle, char const* cmd, ...) {
   va_list ap;
   char local_cmd[GP_CMD_SIZE];
 
@@ -310,6 +310,26 @@ void gnuplot_cmd (gnuplot_ctrl *handle, char *cmd, ...) {
   return;
 }
 
+void send_plot_cmd(gnuplot_ctrl* handle, char* cmd, char const* name, char const* title)
+{
+  char const* command = (handle->nplots > 0) ? "replot" : "plot";
+  if (title)
+    sprintf(cmd, "%s \"%s\" title \"%s\" with %s", command, name, title, handle->pstyle);
+  else
+    sprintf(cmd, "%s \"%s\" notitle with %s", command, name, handle->pstyle);
+  gnuplot_cmd(handle, cmd);
+}
+
+void send_splot_cmd(gnuplot_ctrl* handle, char* cmd, char const* name, char const* title)
+{
+  char const* command = "splot";
+  if (title)
+    sprintf(cmd, "%s \"%s\" title \"%s\" with %s", command, name, title, handle->pstyle);
+  else
+    sprintf(cmd, "%s \"%s\" notitle with %s", command, name, handle->pstyle);
+  gnuplot_cmd(handle, cmd);
+}
+
 /*-------------------------------------------------------------------------*/
 /**
   @brief    Change the plotting style of a gnuplot session.
@@ -330,7 +350,7 @@ void gnuplot_cmd (gnuplot_ctrl *handle, char *cmd, ...) {
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_setstyle (gnuplot_ctrl *handle, char *plot_style) {
+void gnuplot_setstyle (gnuplot_ctrl *handle, char const* plot_style) {
   if (strcmp(plot_style, "lines") &&
       strcmp(plot_style, "points") &&
       strcmp(plot_style, "linespoints") &&
@@ -349,6 +369,12 @@ void gnuplot_setstyle (gnuplot_ctrl *handle, char *plot_style) {
   return;
 }
 
+void gnuplot_append_style (gnuplot_ctrl *handle, char const* plot_style) {
+  int len = strlen(handle->pstyle);
+  strncpy(handle->pstyle + len, plot_style, sizeof(handle->pstyle) - len - 1);
+  return;
+}
+
 /*-------------------------------------------------------------------------*/
 /**
   @brief    Change the terminal of a gnuplot session.
@@ -371,7 +397,7 @@ void gnuplot_setstyle (gnuplot_ctrl *handle, char *plot_style) {
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_setterm (gnuplot_ctrl *handle, char *terminal, int width, int height) {
+void gnuplot_setterm (gnuplot_ctrl *handle, char const* terminal, int width, int height) {
   char cmd[GP_CMD_SIZE];
 
   strncpy(handle->term, terminal, 32);
@@ -399,7 +425,7 @@ void gnuplot_setterm (gnuplot_ctrl *handle, char *terminal, int width, int heigh
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_set_axislabel (gnuplot_ctrl *handle, char *axis, char *label) {
+void gnuplot_set_axislabel (gnuplot_ctrl *handle, char const* axis, char const* label) {
   char cmd[GP_CMD_SIZE];
 
   sprintf(cmd, "set %slabel \"%s\"", axis, label);
@@ -482,14 +508,13 @@ void gnuplot_i_error (gnuplot_ctrl *handle) {
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double *x, double *y, int n, char *title) {
+void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double const* x, double const* y, int n, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
 
   /* Error handling: mandatory arguments, already open session, opening temporary file */
   FAIL_IF (x == NULL || (n < 1), "One of the parameters to gnuplot_plot_coordinates() has been misspecified");
-  gnuplot_i_error(handle);
 
   /* Open temporary file for output */
   sprintf(name, GNUPLOT_TEMPFILE, P_tmpdir);
@@ -501,14 +526,13 @@ void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double *x, double *y, int n
 
   /* Write data to this file */
   for (int i = 0; i < n; i++) {
-    (y == NULL || memcmp(y, y+1, (sizeof(y)-1)*sizeof(y[0])) == 0) ? sprintf(cmd, "%g\n", x[i]) : sprintf(cmd, "%g %g\n", x[i], y[i]);
+    (y == NULL) ? sprintf(cmd, "%g\n", x[i]) : sprintf(cmd, "%g %g\n", x[i], y[i]);
     write(tmpfd, cmd, strlen(cmd));
   }
   close(tmpfd);
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "%s \"%s\" title \"%s\" with %s", (handle->nplots > 0) ? "replot" : "plot", name, (title) ? title : "No title" , handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_plot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -547,7 +571,7 @@ void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double *x, double *y, int n
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_splot (gnuplot_ctrl *handle, double *x, double *y, double *z, int n, char *title) {
+void gnuplot_splot (gnuplot_ctrl *handle, double const* x, double const* y, double const* z, int n, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
@@ -572,8 +596,7 @@ void gnuplot_splot (gnuplot_ctrl *handle, double *x, double *y, double *z, int n
   close(tmpfd);
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "splot \"%s\" title \"%s\" with %s", name, (title) ? title : "No title", handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_splot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -599,7 +622,7 @@ void gnuplot_splot (gnuplot_ctrl *handle, double *x, double *y, double *z, int n
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_splot_grid (gnuplot_ctrl *handle, double *points, int rows, int cols, char *title) {
+void gnuplot_splot_grid (gnuplot_ctrl *handle, double const* points, int rows, int cols, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
@@ -628,8 +651,7 @@ void gnuplot_splot_grid (gnuplot_ctrl *handle, double *points, int rows, int col
   close(tmpfd);
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "splot \"%s\" title \"%s\" with %s", name, (title) ? title : "No title", handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_splot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -672,7 +694,7 @@ void gnuplot_splot_grid (gnuplot_ctrl *handle, double *points, int rows, int col
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_contour_plot (gnuplot_ctrl *handle, double *x, double *y, double *z, int nx, int ny, char *title) {
+void gnuplot_contour_plot (gnuplot_ctrl *handle, double const* x, double const* y, double const* z, int nx, int ny, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
@@ -707,8 +729,7 @@ void gnuplot_contour_plot (gnuplot_ctrl *handle, double *x, double *y, double *z
   gnuplot_cmd(handle, "set view 0,0");
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "splot \"%s\" title \"%s\" with %s", name, (title) ? title : "No title", handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_splot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -733,7 +754,7 @@ void gnuplot_contour_plot (gnuplot_ctrl *handle, double *x, double *y, double *z
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char *title) {
+void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
@@ -760,8 +781,7 @@ void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *
   close(tmpfd);
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "splot \"%s\" title \"%s\" with %s", name, (title) ? title : "No title", handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_splot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -813,14 +833,13 @@ void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *
  */
 /*-------------------------------------------------------------------------*/
 
-void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char *title) {
+void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char const* title) {
   int tmpfd;
   char name[NAME_SIZE];
   char cmd[GP_CMD_SIZE];
 
   /* Error handling: mandatory arguments, already open session, opening temporary file */
   FAIL_IF (getPoint == NULL || (n < 1), "One of the parameters to gnuplot_plot_obj_xy() has been misspecified");
-  gnuplot_i_error(handle);
 
   /* Open temporary file for output */
   sprintf(name, GNUPLOT_TEMPFILE, P_tmpdir);
@@ -840,8 +859,7 @@ void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void
   close(tmpfd);
 
   /* Command to be sent to gnuplot */
-  sprintf(cmd, "%s \"%s\" title \"%s\" with %s", (handle->nplots > 0) ? "replot" : "plot", name, (title) ? title : "No title", handle->pstyle);
-  gnuplot_cmd(handle, cmd);
+  send_plot_cmd(handle, cmd, name, title);
   handle->nplots++;
 }
 
@@ -866,7 +884,7 @@ void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_plot_once (char *style, char *label_x, char *label_y, double *x, double *y, int n, char *title) {
+void gnuplot_plot_once (char const* style, char const* label_x, char const* label_y, double const* x, double const* y, int n, char const* title) {
   /* Define handle as local variable to isolate it from other gnuplot sessions */
   gnuplot_ctrl *handle;
 
@@ -909,10 +927,14 @@ void gnuplot_plot_once (char *style, char *label_x, char *label_y, double *x, do
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_plot_equation (gnuplot_ctrl *handle, char *equation, char *title) {
+void gnuplot_plot_equation (gnuplot_ctrl *handle, char const* equation, char const* title) {
   char cmd[GP_CMD_SIZE];
 
-  sprintf(cmd, "%s %s title \"%s\" with %s", (handle->nplots > 0) ? "replot" : "plot", equation, (title) ? title : "No title", handle->pstyle);
+  char const* command = (handle->nplots > 0) ? "replot" : "plot";
+  if (title)
+    sprintf(cmd, "%s %s title \"%s\" with %s", command, equation, title, handle->pstyle);
+  else
+    sprintf(cmd, "%s %s notitle with %s", command, equation, handle->pstyle);
   gnuplot_cmd(handle, cmd);
   handle->nplots++;
 }
@@ -944,7 +966,7 @@ void gnuplot_plot_equation (gnuplot_ctrl *handle, char *equation, char *title) {
  */
 /*--------------------------------------------------------------------------*/
 
-void gnuplot_hardcopy (gnuplot_ctrl *handle, char *filename, char *color) {
+void gnuplot_hardcopy (gnuplot_ctrl *handle, char const* filename, char const* color) {
   if (color == NULL) {
     gnuplot_cmd(handle, "set terminal postscript");
   } else {
diff --git a/gnuplot_i.h b/gnuplot_i.h
old mode 100755
new mode 100644
index 463e234..2ec1e33
--- a/gnuplot_i.h
+++ b/gnuplot_i.h
@@ -23,6 +23,10 @@
 /** Maximum amount of characters of a temporary file name */
 #define GP_TMP_NAME_SIZE 512
 
+#ifdef __cplusplus
+extern "C" {
+#endif
+
 /*---------------------------------------------------------------------------
   Gnuplot_i types
  ---------------------------------------------------------------------------*/
@@ -47,7 +51,7 @@
 typedef struct _GNUPLOT_CTRL_ {
   FILE *gnucmd;       /*!< Pipe to gnuplot process. */
   int nplots;         /*!< Number of currently active plots. */
-  char pstyle[32];    /*!< Current plotting style. */
+  char pstyle[256];   /*!< Current plotting style. */
   char term[32];      /*!< Save terminal name, used by `gnuplot_hardcopy()` function. */
   char to_delete[GP_MAX_TMP_FILES][GP_TMP_NAME_SIZE];   /*!< Names of temporary files. */
   int ntmp;           /*!< Number of temporary files in the current session. */
@@ -77,29 +81,34 @@ typedef struct _GNUPLOT_POINT_ {
 
 /* Auxiliary functions */
 
-char *gnuplot_get_program_path (char *pname);
+char const* gnuplot_get_program_path (char const* pname);
 void print_gnuplot_handle (gnuplot_ctrl *handle);
 
 /* Gnuplot interface handling functions */
 
 gnuplot_ctrl *gnuplot_init (void);
 void gnuplot_close (gnuplot_ctrl *handle);
-void gnuplot_cmd (gnuplot_ctrl *handle, char *cmd, ...);
-void gnuplot_setstyle (gnuplot_ctrl *handle, char *plot_style);
-void gnuplot_setterm (gnuplot_ctrl *handle, char *terminal, int width, int height);
-void gnuplot_set_axislabel (gnuplot_ctrl *handle, char *axis, char *label);
+void gnuplot_cmd (gnuplot_ctrl *handle, char const* cmd, ...);
+void gnuplot_setstyle (gnuplot_ctrl *handle, char const* plot_style);
+void gnuplot_append_style (gnuplot_ctrl *handle, char const* plot_style);
+void gnuplot_setterm (gnuplot_ctrl *handle, char const* terminal, int width, int height);
+void gnuplot_set_axislabel (gnuplot_ctrl *handle, char const* axis, char const* label);
 void gnuplot_resetplot (gnuplot_ctrl *handle);
 
 /* Gnuplot interface plotting functions */
 
-void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double *x, double *y, int n, char *title);
-void gnuplot_splot (gnuplot_ctrl *handle, double *x, double *y, double *z, int n, char *title);
-void gnuplot_splot_grid (gnuplot_ctrl *handle, double *points, int rows, int cols, char *title);
-void gnuplot_contour_plot (gnuplot_ctrl *handle, double *x, double *y, double *z, int nx, int ny, char *title);
-void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char *title);
-void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char *title);
-void gnuplot_plot_once (char *style, char *label_x, char *label_y, double *x, double *y, int n, char *title);
-void gnuplot_plot_equation (gnuplot_ctrl *handle, char *equation, char *title);
-void gnuplot_hardcopy (gnuplot_ctrl *handle, char *filename, char *color);
+void gnuplot_plot_coordinates (gnuplot_ctrl *handle, double const* x, double const* y, int n, char const* title);
+void gnuplot_splot (gnuplot_ctrl *handle, double const* x, double const* y, double const* z, int n, char const* title);
+void gnuplot_splot_grid (gnuplot_ctrl *handle, double const* points, int rows, int cols, char const* title);
+void gnuplot_contour_plot (gnuplot_ctrl *handle, double const* x, double const* y, double const* z, int nx, int ny, char const* title);
+void gnuplot_splot_obj (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char const* title);
+void gnuplot_plot_obj_xy (gnuplot_ctrl *handle, void *obj, void (*getPoint)(void *, gnuplot_point *, int, int), int n, char const* title);
+void gnuplot_plot_once (char const* style, char const* label_x, char const* label_y, double const* x, double const* y, int n, char const* title);
+void gnuplot_plot_equation (gnuplot_ctrl *handle, char const* equation, char const* title);
+void gnuplot_hardcopy (gnuplot_ctrl *handle, char const* filename, char const* color);
+
+#ifdef __cplusplus
+}
+#endif
 
 #endif