c program

Question

‪#‎include‬<stdio.h>
int main()
{
int a;
char ch;
printf("enter");
scanf("%d",&a);

printf("enter a value");
scanf("%c",&ch);
return 0;
}

why 2nd input not reading?

Answer 1

%C does not skip any leftover whitespace( newline while entering the previous input ). It immediately reads that and returns.

But if we change the order of reading the inputs (char first)

	printf("enter a value");
	scanf("%c",&ch);
	printf("enter");
	scanf("%d",&a);

It works fine.

Possible Solutions :

1. Using an extra white space before %C specifier :

scanf(" %c",&ch);

2. or using getchar() in between to consume any newline feed in the input stream.

#include <stdio.h>
int main() {
int a;
	char ch;
	printf("enter");
	scanf("%d",&a);
	getchar();
	printf("enter a value");
	scanf("%c",&ch);

	return 0;
}

One more possible situation : 

There is a newline after every character in the input file which is consumed in the next iteration:

So to prevent this : using getchar() just after scanf():

Comments

Actually it is not the issue of "%c" not skipping the whitespace but it is the issue of "%d" skipping the whitespace :P We are just used to "%d" and hence expecting same from %c. But when we are telling the computer to read a 'CHARACTER' it must not skip anything.

Answer 2

since after entering a number an enter is pressed which is stored in stdin (keyboard buffer) so ch stores enter and dont need any input

soln either write fflush (stdin) or reverse the order of inputs and everything will be  fine

Comments

Thanks Sir, fflush(stdin) will also do.

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what is fflus(hstdin) and fflush(stdout)

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it is used to clear(flush) the buffer of standard input device(keyboard)

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#include <stdio.h>

 

int main(void)

{

    char c;

    /* FIX: Leave a space before %c */

     

    printf("Input No.1\n");

    scanf(" %c", &c);

    printf("c = %c\n", c);

     

    printf("Input No.2\n");

    scanf(" %c", &c);

    printf("c = %c\n", c);

     

    printf("Input No.3\n");

    scanf(" %c", &c);

    printf("c = %c\n", c);

     

    return 0;

}

what wil happen in above?

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It should work. Why ? not working or what ?

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it will work

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could u expain how it works