Thread: Structs and arrays - overview and help neede

Hi, in my phase of (re)learning C, I'm often facing problems with arrays and structures (and pointers).
This is a little test I wrote.

Code:

#include <stdio.h>
#include <string.h>
#include <stdlib.h>

typedef struct {
    char name[10];
} man;

int main (int argc, const char * argv[]) {
    int i;
    man john;
    strcpy(john.name, "john");

    // array of structures
    man men[10];
    strcpy(men[3].name, "john");
    printf("*** %s ***\n", men[3].name);

    // dynamic array of structures
    man *men2;
    men2 = malloc(10 * sizeof(man));
    strcpy(men2[3].name, "john");
    printf("*** %s ***\n", men2[3].name);

    // multidimensional array of structures
    man men3[10][10];
    strcpy(men3[3][3].name, "john");
    printf("*** %s ***\n", men3[3][3].name);

    // dynamic multidimensional array of structures
    man **men4;
    men4 = malloc(10 * sizeof(man*));
    for (i = 0; i < 10; i++)
        men4[i] = malloc(10 * sizeof(man*));
    strcpy(men4[3][3].name, "john");
    printf("*** %s ***\n", men4[3][3].name);

    // array of pointer to structure
    man *men5[10];
    men5[3] = &john;
    printf("*** %s ***\n", men5[3]->name);

    // dynamic array of pointers to structure
    man **men6;
    men6 = malloc(10 * sizeof(*men6));
    men6[3] = &john;
    printf("*** %s ***\n", men6[3]->name);   

    // dynamic multidimensional array of pointers to structures
    /* ? */

    return 0;
}

Can you:

1. tell me if all is correct
2. explain why in men4 i use sizeof(man*) by in men6 it is sizeof(*men6)
3. explain how to make a dynamic multidimensional array of pointers to structures (last point)
4. explain me men4? it works, but is seems to me more of an array of pointers to structure than a multidimensional array of structures!

Thanks in advance.

thank you very much, elysia, it helped a lot!

is this the correct way of doing the last point?

Code:

	// dynamic multidimensional array of pointers to structures
	man ***men7;
	men7 = malloc(10 * sizeof(man**));
	for (i = 0; i < 10; i++)
		men7[i] = malloc(10 * sizeof(man*));
	men7[3][3] = &john;
	printf("*** %s ***\n", men7[3][3]->name);

thanks again for your interest. i don't think i got it, by the way. the way i read the code i wrote (so that it may be easier for you to understand where i'm wrong, eventually is:

man ***men7;

here i declare an array [of not defined size] to an array [of not defined size] of pointers to to the struct man

men7 = malloc(10 * sizeof(man**));

i allocate the space for 10 pointers to pointers to man, or an array of 10 pointers to pointers to man

for (i = 0; i < 10; i++)
men7[i] = malloc(10 * sizeof(man*));

each of those 10 pointers defined in the step before is allocated the space for 10 [sub] pointers to man

men7[3][3] = &john;

here the 4th pointer to man of the 4th pointer to pointer to man is assigned the address of man "john" defined before

printf("*** %s ***\n", men7[3][3]->name);

and i recall it.

what is the flaw in my logic or understanding of pointers? thank in advance again!

thanks again for your help, it really helped me made some things clearer.