quick guide

Unlike integer numbers,the field width of real
numbers s not to be specified and therefore scanf reads
real numbers using the simple specifications %f for both the
notations,namely decimal point and exponential notation.
Example: scanf(%f%f%f",&x,&y,&z);
input data
475.89 43.21e-1 678
will assign the value 475.89 to x,4.321 to y and
678.0 to z. The input field specifications may be separated
by an arbitrary blank spaces. If the number to be read is
of double type ,then the pecification should be lf% instead
of %f. A number may be skipped using %*f.

Program:
/*Reading of real numbers */
main()
{
float x,y;
double p,q;
printf("values of x and y:");
scanf("%f\n%e",&x,&y);
printf("\n");
printf("x=%f \n y=%f\n\n",x,y);
printf("values of p and q:");
scanf("%lf%lf",&p,&q);
printf("\n p=%lf \n q=%e",p,q);
printf("\n\n p=%12lf \n p=%12e",p,q);
}

Output: values of x and y:12.3456 17.5e-2
x=12.345600
y=0.175000
values of p and q: 4.14285178 18.5678901234567890
p=4.14285178
q=1.856789012346e+00