View Compilation Error

0_0_28746604_10989.c: In function 'main':
0_0_28746604_10989.c:9:51: error: 'EOF' undeclared (first use in this function)
     }while(scanf("%lf%lf%lf%lf",&x1,&y1,&x2,&y2)!=EOF);
                                                   ^
0_0_28746604_10989.c:9:51: note: each undeclared identifier is reported only once for each function it appears in