Why should single space is provided before the format specifier for this given C code?

Question

In this PROGRAM 1 i am not getting the expected output.

// PROGRAM 1
#include <stdio.h>

int main () {
  char str1, str2;

  printf("Enter char1: \n");
  scanf("%c", str1);

  printf("Enter char2: \n");
  scanf("%c", str2);

  printf("Entered char1: %c\n", str1);
  printf("Entered char2:%c\n", str2);

  return(0);
}

In this program i am getting expected output. So pls tell me the reason why not for PROGRAM 1

//PROGRAM 2
#include <stdio.h>

int main () {
  char str1[5], str2[5];

  printf("Enter name: \n");
  scanf("%s", str1);

  printf("Enter your website name: \n");
  scanf("%s", str2);

  printf("Entered Name: %s\n", str1);
  printf("Entered Website:%s\n", str2);

  return(0);
}

As for your problem, I think you need [to read a couple of good beginners books](http://stackoverflow.com/questions/562303/the-definitive-c-book-guide-and-list) first and foremost. — Some programmer dude, Nov 02 '17 at 06:57
"*what is the format specifier for ...*": It's all in the docs: http://man7.org/linux/man-pages/man3/printf.3.html — alk, Nov 02 '17 at 07:16
bro in PROGRAM 1 the scanf statement is not asking the input form the user pls help me in this — Abdulvakaf K, Nov 02 '17 at 09:48
@AbdulvakafK please don't edit the question so as to invalidate existing answers. It's very unhelpful for future users/visitors and annoying for those who gave time to provide answers:( — Martin James, Nov 02 '17 at 10:02
I suspect you want `scanf(" %c", &str1);` (note: & and space) — chux - Reinstate Monica, Nov 02 '17 at 14:22
Hello https://stackoverflow.com/users/2410359/chux Exactly i needed "Space" . ok let me know Why(Please explain detail) ? — Abdulvakaf K, Nov 03 '17 at 05:38

Marievi · Accepted Answer · 2017-11-02T07:05:07.523

scanf needs a pointer as argument. So you should change the scanfs in your first program to :

scanf("%c", &str1);

and

scanf("%c", &str2);

in order to pass the addresses of your variables.

The reason why the second program works is that str1 and str2 in this case are arrays, so when you pass their names as arguments to scanf, you actually pass their addresses. This happens because array names decay to pointers. You can also refer to this answer for more details.

msc · Answer 2 · 2017-11-02T07:04:33.837

1

In first program, %c format specifier print only one character. So, if you want to print only one character then use %c format specifier.

Also, If you scan character type then use &. like scanf("%c",&str2);

In second program, %s format specifier print string. So, if you want to print string then use %s format specifier.

%s no need to & because string buffers are already represented as addresses.

edited Nov 02 '17 at 07:04

answered Nov 02 '17 at 06:57

msc

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1

Didn't you notice the missing `&` in `scnaf` in 1st program. – Sniper Nov 02 '17 at 06:59
2

I think you should also explain why `&` is *not* needed in the second case. – babon Nov 02 '17 at 07:03

Why should single space is provided before the format specifier for this given C code?

2 Answers2