scanf usage

[Philsonpott]

I'm using scanf to scan for simple user input (see below for an example of what I'm doing...), and if I try to use it multiple times to scan for a character, it ignores any try after the first. I have a feeling this has to do with the stdin not being cleared after the input, and it just reads the first input over again, but I have no idea how to fix this. I've read through the explanations of scanf on this and other websites and am still confused.

I want to first figure this out before I move on to trying cin. I think knowing why this isn't working would be very helpful to my understanding of C/C++ as a whole...

#include <stdio.h>

int main() {

char Ans[2];

printf("T/F: Austin is the capital of Texas.\n");

scanf("%c", &Ans[0]);

if(Ans[0] == 'T') 
	{

printf("Correct!");

	}

else 
	{
	
printf("Incorrect");

	}
	
printf("\nT/F: Texas is the Sunshine State.\n");

scanf("%c", &Ans[1]);

if(Ans[1] == 'F')

	{

printf("Correct!");

	}

else 
	{
	
printf("Incorrect");

	}

return 0;

}

[jmc]

The solution to your Problem is actually quite simple.
when u enter a key (or more than one) and press enter you read 2 (or more than 2) characters. Your characters + 1 newline.
Use for example " %c" (as many whitspaces as u want + character) instead of "%c" and u shouldn't have any problems any more.

[Philsonpott]

Well, that certainly fixed the problem, but I'm still not certain I understand why. Is it that when I use "%c" it only wants to read 1 character, but by default when I enter "T" and press enter, there are two characters, and the next scanf is thrown off because of that?

[jmc]

Yes, the next scanf reads 13 as an decimal value the same as \n (newline).
So your input looks like this: "T\n"

scanf("%c", &Ans[0]); // reads T
scanf("%c", &Ans[1]); // reads \n (ENTER) 

If you added a third scanf your program would wait for a new input since it finds only 2 characters but then it would need 3.

scanf("%c", &Ans[0]); // reads T
scanf("%c", &Ans[1]); // reads \n (ENTER)
scanf("%c", &Ans[2]); // wait for a new input 

[Philsonpott]

Thanks, and one last thing:

If someone accidently entered more characters than I had prepped scanf for, it could cause problems the rest of the way, right?

[jmc]

Exactly. Eg

scanf("%c", &Ans[0]); // input ABCDE reads A
scanf("%c", &Ans[1]); // reads B
scanf("%c", &Ans[2]); // reads C
scanf("%c", &Ans[3]); // reads D
scanf("%c", &Ans[4]); // reads E
scanf("%c", &Ans[5]); // reads \n
scanf("%c", &Ans[6]); // wait for new input 

You may want to have a look at getch() (POSIX) or _getch() of the conio.h header file.
Or maybe later _kbhit() for a little more complex usage of console input.