Add first Code

Code/.clang-format

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+---
+Language:             Cpp
+BasedOnStyle:         WebKit
+ColumnLimit:          100
+FixNamespaceComments: true
+...

Code/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.8)
+
+if ( CMAKE_COMPILER_IS_GNUCC )
+    set(CMAKE_CXX_FLAGS  "${CMAKE_CXX_FLAGS} -Wall -Wextra")
+endif()
+
+find_package(OpenGL REQUIRED)
+find_package(GLUT REQUIRED)
+
+add_subdirectory(hello_world)

Code/hello_world/CMakeLists.txt

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+cmake_minimum_required (VERSION 3.8)
+
+add_executable (hello_world helloWorld.c)
+target_include_directories(hello_world PRIVATE ${OPENGL_INCLUDE_DIRS}  ${GLUT_INCLUDE_DIRS} )
+target_link_libraries(hello_world ${OPENGL_LIBRARIES} ${GLUT_LIBRARY} )

Code/hello_world/helloWorld.c

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+#include <GL/glut.h>
+#include <string.h>
+
+int width = 640;
+int height = 480;
+
+void init(int argc, char** argv)
+{
+    glutInit(&argc, argv); // Initialisierung der GLUT Bibliothek
+    glutInitDisplayMode(GLUT_SINGLE); // Initialisierung des Single Buffer Modes
+    glutInitWindowSize(width, height); // Fenstergröße in Pixel (Breite, Hoehe)
+    glutInitWindowPosition(
+        100, 100); // Fensterposition in Pixel, ausgehend vom Ursprung des Window Systems
+    glViewport(0, 0, width, height);
+    glutCreateWindow("Hello world"); // Erstellen des Fensters
+    glMatrixMode(GL_PROJECTION);
+    glLoadIdentity();
+    gluOrtho2D(0, width, 0, height);
+    glMatrixMode(GL_MODELVIEW);
+    glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
+}
+
+void display(void)
+{
+    const char* myText = "Hello World!";
+    int j;
+
+    glClear(GL_COLOR);
+    glColor3f(1.0, 0.0, 0.0);
+
+    glBegin(GL_POLYGON);
+    glVertex3f((width / 2) - (width / 4), (height / 2) - (height / 4), 0.0);
+    glVertex3f((width / 2) + (width / 4), (height / 2) - (height / 4), 0.0);
+    glVertex3f((width / 2) + (width / 4), (height / 2) + (height / 4), 0.0);
+    glVertex3f((width / 2) - (width / 4), (height / 2) + (height / 4), 0.0);
+    glEnd();
+
+    glColor3f(1.0, 1.0, 1.0);
+    glRasterPos2i((width / 2) - (width / 4) + 10, (height / 2) - (height / 4) + 10);
+    for (j = 0; j < strlen(myText); j++) {
+        glutBitmapCharacter(GLUT_BITMAP_HELVETICA_18, myText[j]);
+    }
+
+    glFlush();
+}
+
+int main(int argc, char** argv)
+{
+    init(argc, argv);
+    glutDisplayFunc(display); // Callback-Funktion für das Fenster
+    glutMainLoop(); // Abgabe der Kontrolle an GLUT-Bibliothek
+    return 0;
+}