OpenGl program - shows only black screen - opengl

Question

I tried simple openGl program to draw triangle, i am able to see only black screen on window.
Below is the code for your reference.
Let me know what i am doing wrong.
// Headers
#include <GL/glew.h>
#include <GL/glut.h>//Drawing funciton
#include <GL/freeglut.h>
// Link statically with GLEW
#define GLEW_STATIC
// Shader sources
const GLchar* vertexSource =
"##version 300 es\n"
"in vec2 position;"
"void main()"
"{"
" gl_Position = vec4(position, 0.0, 1.0);"
"}";
const GLchar* fragmentSource =
"##version 300 es\n"
"out vec4 outColor;"
"void main()"
"{"
" outColor = vec4(1.0, 1.0, 1.0, 1.0);"
"}";
int main(int argc,char**argv)
{ glutInit(&argc, argv);
glutInitDisplayMode(GLUT_RGB | GLUT_DEPTH | GLUT_DOUBLE);
glutInitWindowSize(800,600);
glutCreateWindow("GW");
//glutSetOption(GLUT_ACTION_ON_WINDOW_CLOSE,GLUT_ACTION_GLUTMAINLOOP_RETURNS);
// Initialize GLEW
glewExperimental = GL_TRUE;
glewInit();
// Create Vertex Array Object
GLuint vao;
glGenVertexArrays(1, &vao);
glBindVertexArray(vao);
// Create a Vertex Buffer Object and copy the vertex data to it
GLuint vbo;
glGenBuffers(1, &vbo);
GLfloat vertices[] = {
0.0f, 0.5f,
0.5f, -0.5f,
-0.5f, -0.5f
};
glBindBuffer(GL_ARRAY_BUFFER, vbo);
glBufferData(GL_ARRAY_BUFFER, sizeof(vertices), vertices, GL_STATIC_DRAW);
// Create and compile the vertex shader
GLuint vertexShader = glCreateShader(GL_VERTEX_SHADER);
glShaderSource(vertexShader, 1, &vertexSource, NULL);
glCompileShader(vertexShader);
// Create and compile the fragment shader
GLuint fragmentShader = glCreateShader(GL_FRAGMENT_SHADER);
glShaderSource(fragmentShader, 1, &fragmentSource, NULL);
glCompileShader(fragmentShader);
// Link the vertex and fragment shader into a shader program
GLuint shaderProgram = glCreateProgram();
glAttachShader(shaderProgram, vertexShader);
glAttachShader(shaderProgram, fragmentShader);
glBindFragDataLocation(shaderProgram, 0, "outColor");
glLinkProgram(shaderProgram);
glUseProgram(shaderProgram);
// Specify the layout of the vertex data
GLint posAttrib = glGetAttribLocation(shaderProgram, "position");
glEnableVertexAttribArray(posAttrib);
glVertexAttribPointer(posAttrib, 2, GL_FLOAT, GL_FALSE, 0, 0);
bool running = true;
while (running)
{
// Clear the screen to black
glClearColor(0.0f, 0.0f, 0.0f, 1.0f);
glClear(GL_COLOR_BUFFER_BIT);
// Draw a triangle from the 3 vertices
glDrawArrays(GL_TRIANGLES, 0, 3);
// Swap buffers
glutSwapBuffers();
}
glDeleteProgram(shaderProgram);
glDeleteShader(fragmentShader);
glDeleteShader(vertexShader);
glDeleteBuffers(1, &vbo);
glDeleteVertexArrays(1, &vao);
return 0;
}