Question

#include<stdio.h>

int main()
{
    char a, b;
    scanf("%c", &a);
    scanf("%c", &b);

    printf("%c %c",a,b);
    return 0;
}

When I run this program, I only get output as a & I don’t get the prompt to enter 2nd character. Why?

Answer 1

In this line,

scanf("%c", &a);

you are actually taking a %d from the stdin (standard input) but at the time you entered a character from stdin, you also typed ENTER from your keyboard which means that now you have two characters in stdin; the character itself & \n. So, the program took first character as the one you entered & second character as \n.

You need to use

scanf("%c\n", &a);

so that scanf eats the newline (that came by pressing ENTER) too.

As rodrigo suggested, you can use these too.

scanf(" %c", &a); or scanf("%c ", &a);

The way you are thinking that second character is printed is wrong. It’s actually being printed but it’s \n so your prompt might be coming to the next line.

Your code will work if you enter both characters without using ENTER.

shadyabhi@archlinux /tmp $ ./a.out 
qw
q wshadyabhi@archlinux /tmp $

Note, when you used this, the only thing in STDIN was q & w. So, the first scanf ate q & the second one w.