Reason of output in C program ?

What is the reason of following output in C program ?
#include<stdio.h>
#include<conio.h>
void main()
{
int a,b,sum;
clrscr();
printf("Enter 1st number");
scanf("%d",&a);
printf("Enter 2nd number:");
scanf("%d",&b);
sum=a+b;
printf("The sum of 2 numbers are %d",sum);
getch();
}
Output
Enter 1st number 5 6
Enter 2nd numberThe sum of 2 numbers are 11

When i am providing 5 and 6 on the same line, then instead of waiting for the 2nd number it is jumping directly to the next message as given above.

It doesn't have to wait for the second number since you've already entered it. If you want it to wait, then don't enter the second number until after the second prompt.

Standard input is line buffered so that scanf() does not return anything until there is a <newline> in the input buffer.

For scanf() whitespace is a field delimiter, so the scanf() call consumes the first value, leaving the second buffered. On the second scanf() call, it returns immediately because there is a <newline> already buffered. Note that the <newline> is not consumed by %d, so a subsequent input call will also return immediately.

One Solution:



Ideally you would wrap the input and buffer flushing into a single function to avoid repetition:

then