Creating a Rainbow using Graphics Programming in C

// A C program to make a rainbow. This program would only
// work in Turbo C compiler in DOS compatible machine
#include<stdio.h>
#include<graphics.h>
#include<dos.h>

// function for making of rainbow
void rainbow()
{
    // auto detection
    int gdriver = DETECT,gmode;
    int x, y, i;

    // initialize graphics mode(passed three arguments to
    // initgraph function)
    // &gdriver is the address of gdriver variable, &gmode is
    // the address of gmode and
    //  "C:\\Turboc3\\BGI" is the directory path where BGI files are stored
    initgraph(&gdriver,&gmode,"C:\\Turboc3\\BGI");

    x = getmaxx() / 2;//finding centre x-ordinate of screen
    y = getmaxy() / 2;//finding centre y-ordinate of screen

    for (i=30; i<200; i++)
    {
        // delay function under dos.h for holding the
        // function for some time
        delay(100);

        // selecting  color for making of rainbow
        setcolor(i/10);

        // making of arc with fixed centre and increasing radius
        arc(x, y, 0, 180, i-10);
    }
}
// driver program
int main()
{
    rainbow();
    return 0;
}