Scanf is not scanning

Answer 1

The problem is that you are leaving the \n entered after the numbers unconsumed and then is read by the second scanf(). If you check the value in opr you'll see it's '\n'.

Answer 2

The second program do take the \n as the character.
Maybe you simply didn't input \n before inputting other characters.

example ( %c in printf is changed to %d to make it clear)

Answer 3

Try adding fflush(stdin) before scanf.

Answer 4

Every time you use scanf with this format :

scanf("%c",&a); 

it leaves a newline which will be consumed in the next iteration. Th last program that you mentioned have only one "scanf". try to use another scanf. you will get the same problem.

so to avoid white spaces you have to write :

 scanf(" %c",&opr); 

the space before the format string tells scanf to ignore white spaces. Or its better to use

getchar();

It will consume all your newline