String termination - char c=0 vs char c='\0'

'\0' is just an ASCII character. It is the same as 'A', or '0' or '\n'.
If you write char c = '\0', it's the same as char c = 0;. If you write char c = 'A', it's the same as char c = 65.

It's just a character representation and it's a good practice to write it, when you really mean the NULL byte of string. Since char is one byte in C (integral type), it doesn't have any special meaning.

The preferred choice is that which can give people reading your code an ability to understand how do you use your variable, as a number or as a character.

The best practice is to use 0 when you mean your variable as a number and to use '\0' when you mean your variable is a character.

The previous answers are already quite clear. I just share what I learned about this issue with a demo.

#include <stdlib.h>
#include <stdio.h>


char*
mystrcat(char *dest, char *src) {
    size_t i,j;
    for(i = 0; dest[i] != '\0'; i++)
        ;
    for(j = 0; src[j] != '\0'; j++)
        dest[i+j] = src[j];
    dest[i+j] = '\0';
    return dest;
}

int main() {
    char *str = malloc(20); // malloc allocates memory, but it doesn't initialize the memory
    // str[0] = '\0';
    str[0] = 0;
    for (int k = 0; k <10; k++) {
        char s[2];
        sprintf(s, "%d", k);
        mystrcat(str, s);
    }
    printf("debug:%s\n", str);
    return 0;
}

In the above program, I used malloc to initialize the pointer, but malloc doesn't initialize the memory. So after the mystrcat operation (which is nearly the same as the strcat function in glibc), the string may contain messy code (since the memory content is not initialized).

So I need to initialize the memory. In this case, str[0] = 0 and str[0] = 0 both can make it work.