Program that prints out the initials of a given name
Your code is buggy. It might seem to work, but accessing name[-1] invokes undefined behavior. You do that in the first iteration of the for loop. To fix it, start at i = 1 instead of i = 0.

The next instance of undefined behavior is when you call toupper(name[i]). The functions from &lt;ctype.h&gt; must not be called with a char as their argument. It must always be an unsigned char or the value of the macro EOF. To fix this, call toupper((unsigned char) name[i]).

The proper type for array indexes is not int, but size_t. Therefore the loop should start with for (size_t i = 1, n = strlen(name).

You have a typo: firts instead of first.

Other than that, the code looks good. In some months you will be able to remove all the comments because they are obvious to you. But until then, they should stay.

To make your program even more correct, you could change the condition name[i - 1] == ' ' to be more precise: !isalpha((unsigned char) name[i - 1]) &amp;&amp; isalpha((unsigned char) name[i]). Then you won't print an "uppercase space" if the input contains several spaces in a row.