C string, char and pointers -

i have misunderstanding respect following concepts in c.

to define string can 1 of following afaik :

define array of chars 1 here :

char array[]; 

or define string char array. let 1 :

char * str, 

why see books using pointers method while others use normal definitions ?

a short answer won't question justice. you're asking 2 of significant, misunderstood, aspects of c.

first of all, in c, definition, string an array of characters, terminated nul character, '\0'.

so if say

char string1[] = "hello"; 

it's if had said

char string1[] = {'h', 'e', 'l', 'l', 'o', '\0'}; 

when use string constant "hello" in program, compiler automatically constructs array you, convenience.

next have character pointer type, char *. called "string char array", it's pointer single char. people refer char * being c's "string type", , in way is, can misleading thing say, because not every char * string, , more importantly c has few mechanisms automatically managing strings you. (what mean that, in c, can't sling strings around if basic data type, can in c++ or basic. typically have worry they're stored, how they're allocated.)

but let's go definition of string. if string array of characters, why pointer characters useful manipulating strings @ all? , answer is, pointers useful manipulating arrays in c; pointers @ manipulating arrays seems if are arrays. (but don't worry, they're not.)

i can't delve full treatise on relationship between arrays , pointers in c here, couple of points must made:

if like

char *string2 = "world"; 

what happens (what compiler automatically) if had written

static char __temporaryarray[] = "world"; char *string2 = __temporaryarray; 

and, actually, since string2 pointer character (that is, points @ characters, not whole arrays of characters), it's really:

char *string2 = &__temporaryarray[0]; 

(that is, pointer points array's first element.)

so since string array, when mentioned string "world" in context weren't using initialize array. c went ahead , created array you, , made pointer point it. c whenever have string constant lying around in program. can later say

string2 = "sailor"; 

and can things like

if(strcmp(string1, "goodbye") == 0) { ... } 

just don't do

char *string3;  strcpy(string3, "rutabaga");        /* wrong!! *// 

that's wrong, , won't work reliably @ all, because nobody allocates memory string3 point to, strcpy copy string into.

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so answer question, see strings created or manipulated if arrays, because that's are. see them manipulated using pointers (char *), because can extremely convenient, long know doing.