Write a C function void words(const char str[ ]) that takes a zero-terminated string as an input, and shows every word of the string on a different line. A word is defined as a sequence of non-space character separated by one or more space characters.

Sure! Here's the implementation of the `words` function in C:

#include <stdio.h>

void words(const char str[]) {
    int i = 0;
    
    while (str[i] != '\0') {
        // Skip leading spaces
        while (str[i] == ' ') {
            i++;
        }
        
        // Print the word
        while (str[i] != ' ' && str[i] != '\0') {
            printf("%c", str[i]);
            i++;
        }
        
        // Move to the next line
        printf("\n");
    }
}

You can use this function to show every word of a string on a different line. For example:

int main() {
    const char str[] = "Hello  world!  This is  a test.";
    words(str);
    return 0;
}

Output:

Hello
world!
This
is
a
test.

Please note that consecutive spaces are treated as a single separator between words.