Use keyboard input to change background colour of screen.

background.cpp

/* Program 3-1
Use keyboard input to change background colour of screen.
*/ 
#include <stdlib.h> 
#include <stdio.h> 
#include <math.h> 
#include <GL/glut.h>
#define KEY_ESC 27 /* GLUT doesn't supply this */
int myrandom(int m) {

	return rand()%m;

}

GLvoid display( GLvoid ) {
/* Do all your OpenGL rendering here */ 
	glClear(GL_COLOR_BUFFER_BIT); 
	glFlush();
}

void keyboard(unsigned char key, int x, int y)
{

  switch (key)
  {
  case 27:             // ESCAPE key
	  exit (0);
	  break;
  case 32:

	  glClearColor((double)myrandom(255)/255, (double)myrandom(255)/255, (double)myrandom(255)/255, (double)myrandom(255)/255);
      glutPostRedisplay();
	  break;
  }
}

void init(){
	glClearColor(1.0,1.0,0.0,1.0);
}

int main(int argc, char* argv[]) {
	GLint width; 
	GLint height;
	glutInit(&argc, argv); 
	glutInitDisplayMode(GLUT_SINGLE | GLUT_RGB);
	width = glutGet(GLUT_SCREEN_WIDTH); 
	height = glutGet(GLUT_SCREEN_HEIGHT);
	glutInitWindowPosition(width/4, height/4); 
	glutInitWindowSize(width/2, height/2); 
	glutCreateWindow(argv[0]);
	glutDisplayFunc(display); 
	glutKeyboardFunc(keyboard);
	init();
	glutMainLoop(); 
	return 0;
}