Program to implement Cohen-Sutherland Line Clipping Algorithm in C++

 /* Program to implement Cohen-Sutherland Line Clipping Algorithm in C++   */

#include<iostream>
#include<graphics.h> //graphics.h library is used to include  graphical operations in a program.
using namespace std;

static int LEFT=1,RIGHT=2,BOTTOM=4,TOP=8,xmin,ymin,xmax,ymax;
             // getcode fun to find out code of end points of line
int getcode(int x,int y) //x,y cordinates of first endpoint of line
{
    int code = 0;
    //Perform Bitwise OR to get outcode
    if(y > ymax) code |=TOP;
    if(y < ymin) code |=BOTTOM;
    if(x < xmin) code |=LEFT;
    if(x > xmax) code |=RIGHT;
    return code;
}
       int main()
{
    int gd = DETECT,gm;//Initialize the variables for the graphics driver and graphics mode
                           // gm is Graphics mode which is a computer display mode that generates image using pixels.
                          // DETECT is a macro defined in "graphics.h" header file
    
        cout<<"Enter the window's minimum and maximum values: ";
    cin>>xmin>>ymin >>xmax>>ymax;
        
        int x1,y1,x2,y2;
    cout<<"Enter the endpoints of the line: ";
    cin>>x1>>y1>>x2>>y2;
        
        initgraph(&gd,&gm,NULL); //initgraph initializes the graphics system by loading a graphics driver from disk
        
       rectangle(xmin,ymin,xmax,ymax); // draw rectanguler window
        
        setcolor(BLUE);
    line(x1,y1,x2,y2);       //Draw line to be clipped
    
    int outcode1=getcode(x1,y1), outcode2=getcode(x2,y2);
    int accept = 0;     //decides if line is to be drawn
    while(1){
        float m =(float)(y2-y1)/(x2-x1);
        //Both points inside. Accept line
    if(outcode1==0 && outcode2==0){ //The logical AND operator (&&) returns true if both operands are true and returns false otherwise.
            accept = 1;
            break;
        }
        //bitwise AND of both codes != 0.Line is outside. Reject line
        else if((outcode1 & outcode2)!=0){
            break;
        }else{
            int x,y,temp;
            //Decide if point1 is inside, if not, calculate intersection
            if(outcode1==0)
                temp = outcode2;
            else
                temp = outcode1;
            //Line clips top edge
            if(temp & TOP){     //if bitwise of temp and top is true
                x = x1+ (ymax-y1)/m; //using this formula perform intersection with top boundry
                y = ymax;
            }
            else if(temp & BOTTOM){     //Line clips bottom edge
                x = x1+ (ymin -y1)/m;
                y = ymin ;
            }else if(temp & LEFT){     //Line clips left edge
                x = xmin;
                y = y1+ m*(xmin-x1);
            }else if(temp & RIGHT){     //Line clips right edge
                x = xmax;
                y = y1+ m*(xmax-x1);
            }
            //Check which point we had selected earlier as temp, and replace its co-ordinates
            if(temp == outcode1){
                x1 = x;
                y1 = y;
                outcode1 = getcode(x1,y1);
            }else{
                x2 = x;
                y2 = y;
                outcode2 = getcode(x2,y2);
            }
        }
    }

    cout<<"After clipping:";
    if(accept)
                 cleardevice();
                setcolor(WHITE);
                rectangle(xmin,ymin,xmax,ymax);     
                setcolor(RED);
        line(x1,y1,x2,y2);
               
    getch();
    closegraph();

return 0;
}