Scanf_s problem

Question

When I built resolution, it has no error, as I input "dmf" random three character, this happened.

Answer 1

Documentation is your friend. The docs here - scanf-s-scanf-s-l-wscanf-s-wscanf-s-l say "Unlike scanf and wscanf, scanf_s and wscanf_s require you to specify buffer sizes for some parameters. Specify the sizes for all c, C, s, S, or string control set [] parameters. The buffer size in characters is passed as an additional parameter. It immediately follows the pointer to the buffer or variable."

So the code should be -

#include <stdio.h>  
  
int main()  
{  
    char a, b, c;  
    scanf_s("%c%c%c", &a, 1, &b, 1, &c, 1);  
    return 0;  
}