initial pointer [expert c]

initial differece between pointer and array

Both arrays and pointers can be initialized with a literal string in their definition. Although these cases look the same, different things are happening. A pointer definition does not allocate space for what's pointed at, only for the pointer, except when assigned a literal string. For example, the definition below also creates the string literal:

char *p = "breadfruit";
Note that this only works for a string literal. You can't expect to allocate space for, for example, a float literal:
                                   float *pip = 3.141;     /* Bzzt! won't compile */

A string literal created by a pointer initialization is defined as read-only in ANSI C; the program will  exhibit undefined behavior if it tries to change the literal by writing through p. Some implementations put string literals in the text segment, where they will be protected with read-only permission.

eg:          char *s = "hello world";

*s = 'w';

would generate an error when running the program.

An array can also be initialized with a string literal:
                          char a[] = "gooseberry";
     In contrast to a pointer, an array initialized by a literal string is writable. The individual characters can later be changed. The following statement:

strncpy(a, "black", 5);
gives the string in the array the new value "blackberry".