Question

I´ve just seen multidimensional arrays and as practice I first wanted to print out a string with this code; alas it didn´t work.

#include <stdio.h>
main()
{
 char a[][20] = {"Hello"};
 printf("%s" , a [1]);
 getchar();
}

The only way I managed doing this was with a adding each character with a loop:

#include <stdio.h> 
main()
{
char a[] = {"Hello"};
int i=0
while(a[i]!='\0')
 {
  printf("%c" , a[i]);
   i++;
  }
getchar();
}

What am I missing when initialising the string?

Answer 1

In the first fragment, you are accessing memory that’s out of bounds. The code that would work is:

#include <stdio.h>
int main(void)
{
    char a[][20] = {"Hello"};
    printf("%s\n", a[0]);
    getchar();
}

C arrays are indexed from zero. You only defined and initialized a[0]; therefore, accessing a[1] is undefined behaviour.

In your second example, you could use "%s" OK:

#include <stdio.h> 
int main(void)
{
    char a[] = {"Hello"};
    printf("%s\n", a);
    getchar();
}

Or you could use:

    printf("%s\n", &a[0]);

This is, of course, a single dimensional array.