my first Graphic Design

#include <GLUT/glut.h>
#include <stdio.h>
#include <stdlib.h>
#include <math.h>

GLenum errorCheck()
{
    GLenum code;
    const GLubyte *string;
    code = glGetError();
    if (code != GL_NO_ERROR)
    {
        string = gluErrorString(code);
        fprintf(stderr, "OpenGL error:  %s\n", string);
    }
    return code;
}

void init(void)
{
    glClearColor(1.0, 1.0, 1.0, 0.0);   // Set display-window color to white;
    glMatrixMode(GL_PROJECTION);        // Set Projection parameters
    gluOrtho2D(0.0, 200.0, 0.0, 150.0); // Specifies an orthogonal projection is to be used to the screen
}

void lineSegment(void)
{
    glClear(GL_COLOR_BUFFER_BIT); // Clear the display window
    glColor3f(0.0, 0.4, 0.2);     // Set line segment color to green

    glBegin(GL_LINES); // Cartesian endpoint coordinates
    glVertex2i(180, 15);
    glVertex2i(10, 145);
    glEnd();
    glFlush(); // proceed all OpenGL routines as quickly as possible
}

int main(int argc, char **argv)
{
    glutInit(&argc, argv);
    glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
    glutInitWindowPosition(50, 100);
    glutInitWindowSize(400, 300);
    glutCreateWindow("An Example OpenGL Program");

    init();
    glutDisplayFunc(lineSegment);
    glutMainLoop();
    return 0;
}