OpenGL program doesn't stop taking input and doesn't display Output - c

Question

//Program to implement Basic Incremental Algorithm
//Working on ubuntu
#include <GL/glut.h>
#include<stdlib.h>
#include <stdio.h>
GLfloat x0,x1,y0,y1; //Input variables taken as global
int flag=1; //variable for display1()
void init(void)
{
glClearColor(0.0,0.0,0.0,0.0);
glMatrixMode(GL_PROJECTION);
glLoadIdentity();
gluOrtho2D(0.0,500.0,0.0,500.0);
}
void PutPixel(GLfloat x,GLfloat y)
{
glBegin(GL_POINTS);
glVertex2f(x,y); //To display pixels on-screen
glEnd();
glFlush();
}
void display1(void)
{
if (flag==1)
{
glClear(GL_COLOR_BUFFER_BIT);
glColor3f(0.7,1.0,1.0);
GLfloat m,c,y;
GLfloat i; //BIA algorithm
m=(y1-y0)/((float)(x1-x0));
c=y1-m*x1;
for (i=x0; i<=x1; i+=0.01)
{
y=c+m*i;
PutPixel(i,y);
}
flag++;
}
}
void Input()
{
printf("Enter the co-ods\n");
scanf("%f %f",&x0,&y0);
scanf("%f %f",&x1,&y1);
}
int main(int argc, char **argv)
{
Input();
glutInit(&argc,argv);
glutInitDisplayMode(GLUT_SINGLE|GLUT_RGBA);
glutInitWindowSize(500,500);
glutInitWindowPosition(100,100);
glutCreateWindow("BIA");
init();
glutDisplayFunc(display1);
glutMainLoop();
return 0;
}
I have initailaized flag as a global variable in the beginning and set it to 1. flag is used in the display1() to ensure that it executes only once. This is just one way I was trying to ensure that the output gets displayed.
Can anyone, please HELP!
Why doesn't the program stop taking input ?

Answer 1

It's working. I'm still unsure about which edit or change bought about it. But it's working!! it's displaying some output