Why %d is require before entering character?

Question

I have tried following code there is require %d before entering character. That is an after switch loop in code.

#include<stdio.h>
#include<conio.h>
void sum();
void mul();
void main()
{
char ch;
int c;
clrscr();
do
{
    printf("\n\n Enetr choice ");
    printf("\n\n\t 1: SUM \n\n\t 2: MUL");
    scanf("\n\n\t %d",&c);
    switch(c)
    {
        case 1:
            sum();
            break;
        case 2:
            mul();
            break;
        default:
            printf("\n\n hhhh..... ");
    }
    printf("\n\n Want u calcualte again");
    //scanf("%d");
    scanf("%c",&ch);
    printf("\n ch value is %c",ch);
}while(ch=='y'|| ch=='Y');
getch();
}
void sum()
{
int s;
s=10+50;
printf(" SUM: %d",s);
}
void mul()
{
int s;
s=10*50;
printf(" SUM: %d",s);
}

Here in this code after switch I tried to input character but without the scanf statement which is in comment is require while you input character. without that scanf statement compiler does not take character input. so please give me solution.

Possible duplicate of http://stackoverflow.com/questions/8464620/program-doesnt-wait-for-user-input-with-scanfc-yn — Manoj Awasthi, Aug 25 '13 at 05:09
As shown in the solution to above issue you can also replace `scanf("%c",&ch);` with `scanf("%c",&ch); // <== replace with " " in format specifier` to eat up the newline. — Manoj Awasthi, Aug 25 '13 at 05:11

score 6 · Answer 1 · answered Aug 25 '13 at 05:09

6

Its because you have to "eat up" the newline from previous input

You don't have to use %d.

Instead use:

while((c = getchar()) != '\n' && c != EOF) ;

in place of

//scanf("%d");

to discard the newline.

answered Aug 25 '13 at 05:09

P0W

46,614
9
72
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score 2 · Accepted Answer · answered Aug 25 '13 at 05:34

2

this is the problem occurred due to the insertion of next line character i.e. '\n' instead of following statement

scanf("%c",&ch);

you should use

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

Now what will happen firstly control goes to new line and then it will insert or input the character, just change this statement you will find your program execute properly...

answered Aug 25 '13 at 05:34

Vaibhav

136
1
3
13

Whitespace characters in scanf format strings do not behave the way you think they do. – mlp Aug 25 '13 at 11:39

score 1 · Answer 3 · edited May 23 '17 at 12:21

1

You have to consume new line character. You can add space before %c in your scanf statement to ignore white space

You should change

scanf("%c",&ch);

to

scanf(" %c",&ch);//this makes scanf ignore white spaces like new line, space etc.

or use getchar() to do it.

c=getchar();

For more insight go to question:
scanf() function doesn't work?

edited May 23 '17 at 12:21

Community

1
1

answered Aug 25 '13 at 05:14

Himanshu Pandey

726
5
13

score 0 · Answer 4 · answered Aug 25 '13 at 06:50

0

Another method that tells scanf to consume or recognize white space (and a new line is considered white space) is to code:

  char ch[2];
  ...
  scanf("%1s", &ch);
  ...
  if (ch[0] == 'x' etc.

answered Aug 25 '13 at 06:50

JackCColeman

3,777
1
15
21

Why %d is require before entering character?

4 Answers4