Difference between using character pointers and character arrays

Question

Basic question.

char new_str[]=\"\";

char * newstr;

If I have to concatenate some data into it or use string functions like strcat/substr/

Answer 1

This is a character array:

char  buf [1000];

So, for example, this makes no sense:

buf = &some_other_buf;

This is because buf, though it has characteristics of type pointer, it is already pointing to the only place that makes sense for it.

char *ptr;

On the other hand, ptr is only a pointer, and may point somewhere. Most often, it's something like this:

ptr = buf;              // #1:  point to the beginning of buf, same as &buf[0]

or maybe this:

ptr = malloc (1000);    // #2:  allocate heap and point to it

or:

ptr = "abcdefghijklmn"; // #3:  string constant

For all of these, *ptr can be written to—except the third case where some compiling environment define string constants to be unwritable.

*ptr++ = 'h';          // writes into #1: buf[0], #2: first byte of heap, or
                       //             #3 overwrites "a"
strcpy (ptr, "ello");  // finishes writing hello and adds a NUL