Any one that can help?

[nullifyed]

Hey, i want to ask something: in the red points do we need " & "? and why?

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>



struct school{

        int age;

        int name[30];

};


void fuc_age(struct school A, int z){
	int i, n;	
		/* Initializing age */    		    
		for(i=0; i<n; i++){

             		printf("Type your age:\n");

             		scanf("%d", &A[i].age);

    		}
}


void fuc_name(struct school A, int z){
	int i, n;
		for(i=0; i<n; i++){
			printf("Type your name:\n");
			scanf("%s", &A[i].name);
		}
}

int main(void){

	
	int i, n;

	struct school *A;

    

    		printf("Please type n:\n");

    		scanf("%d", &n);            


    		A = (struct school *)malloc(n*sizeof(struct school));


		/* Print the A... */

    		for(i=0; i<n; i++){

             		printf("Name: %s, Age: %d\n", A[i].name, A[i].age);

    		}

    

    	//system("pause");

    	return 0;

}

[Adak]

scanf() needs the address of a variable, if it is to change the value of that variable. Contrast this with printf(), which doesn't need the address of a variable, because it merely prints it, and doesn't change it in any way.

[nullifyed]

this is the output if i put the adresses:
file4.c: In function ‘fuc_age’:
file4.c:16: error: subscripted value is neither array nor pointer
file4.c: In function ‘fuc_name’:
file4.c:24: error: subscripted value is neither array nor pointer
file4.c: In function ‘main’:
file4.c:40: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘int *’

The A[i].age isn' t int?

[MK27]

Presuming you intend to submit a struct via a parameter to get filled in, you would want those function prototypes to be:

void fuc_age(struct school *A, int z);
void fuc_name(struct school *A, int z);

indicating a pointer. With that you would use:

scanf("%d", &(A->age));
scanf("%s", A->name);

In the first case, struct school member age is an int, so we have the address of operator (&) and the int in question, A->age. -> is "indirect" or pointer notation (since A is a pointer).

In the second case A->string is itself a pointer (or rather, an array name, but it serves as a pointer here), so no & is needed.

You have some problems in those function definitions:

void fuc_name(struct school A, int z){
	int i, n;
		for(i=0; i<n; i++){

n is not initialized to any particular value.

[nullifyed]

I just found one more mistake...but there is one problem...
output:
file4.c: In function ‘fuc_name’:
file4.c:24: warning: format ‘%s’ expects type ‘char *’, but argument 2 has type ‘char (*)[30]’

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <time.h>



struct school{

        int age;

        char name[30];

};


void fuc_age(struct school A[], int z){
	int i, n;	
		/* Initializing age */    		    
		for(i=0; i<n; i++){

             		printf("Type your age:\n");

             		scanf("%d", &A[i].age);

    		}
}


void fuc_name(struct school A[], int z){
	int i, n;
		for(i=0; i<n; i++){
			printf("Type your name:\n");
			scanf("%s", &A[i].name);
		}
}

int main(void){

	
	int i, n;

	struct school *A;

    

    		printf("Please type n:\n");

    		scanf("%d", &n);            


    		A = (struct school *)malloc(n*sizeof(struct school));


		/* Print the A... */

    		for(i=0; i<n; i++){

             		printf("Name: %s, Age: %d\n", A[i].name, A[i].age);

    		}

    

    	//system("pause");

    	return 0;

}

[MK27]

...but there is one problem...

Hopefully you noticed my last post which should address that issue.

[nullifyed]

Can i ask something..." -> " is nessecary? i mean if we do not use this and use sth else insteed, can the code be right, compile and run?

Add: I noticed the last post now and thank you it compiled ! we were writing simultaneously...i still can' t get in my mind this " ->"...and i also have some other questions:
Which is the difference between the 2 red points? i know that we can' t use both of them simultaneously...so i want you to tell me when we use [ ] and when *?

fuction(struct example *A[] ){

also in this code, can you explain the diference:
1) scanf("%d", &(A[i].age));
2) scanf("%d", &(A->.age)); where is " i "? is it correct ? the point A direct only in the first cell af the array...right? so what happens with the rest?

scanf("%d", &(A->age));
scanf("%s", A->name);

[KBriggs]

use sth else insteed,

like what?

[nullifyed]

like what?

such as &... wrong?

insteed of:

scanf("%d", &(A->age));

if i write:

scanf("%d", &A[i].age);

what will happen apart from the error? i mean, what exactly did i wrote and how the scanf will operate?

[MK27]

what will happen apart from the error? i mean, what exactly did i wrote and how the scanf will operate?

If it is an error, what will happen apart from that does not matter too much. If it compiles and works, I guess you should be able to find evidence of something.

[nullifyed]

Can i ask something..." -> " is nessecary? i mean if we do not use this and use sth else insteed, can the code be right, compile and run?

Add: I noticed the last post now and thank you it compiled ! we were writing simultaneously...i still can' t get in my mind this " ->"...and i also have some other questions:
Which is the difference between the 2 red points? i know that we can' t use both of them simultaneously...so i want you to tell me when we use [ ] and when *?

fuction(struct example *A[] ){

also in this code, can you explain the diference:
1) scanf("%d", &(A[i].age));
2) scanf("%d", &(A->.age)); where is " i "? is it correct ? the point A direct only in the first cell af the array...right? so what happens with the rest?

scanf("%d", &(A->age));
scanf("%s", A->name);

i 'll be glad if somebody could explain these to me...

[claudiu]

There's nothing to explain really, I think I provided you with an example in another thread. If you are using a POINTER to a struct you need to access its members using the little arrow -> . In your case A is an array of structs so you would access each member like so: A[i].age . However, if you had an array of pointers to structs you would use A[i]->age, REPLACING the DOT with ARROW.

No, there is no way around this unless you want to mess around with defines which doesn't seem like a good idea. Why don't you want to use the arrow; if anything it makes the code more readable because you know that variable is a pointer without looking at the declaration.

[nullifyed]

So, if i am right, the only change that i have to made is the red point.

void fuc_age(struct school A[ ], int z){

and inside the fuction, this is ok...

scanf("%d", &A[i].age);
scanf("%s", A[i].name);

Am i wrong?

[claudiu]

You have to Google and read about the difference between pointers and arrays either on this site or somewhere else. I feel like this will help you out understanding the source of your confusion a little better.

As for the change, assuming that you are adding what is in red, then yes that should work.

[MK27]

where is " i "? is it correct ? the point A direct only in the first cell af the array...right? [...]i 'll be glad if somebody could explain these to me...

Gosh, that was my fault for reading too quickly, sorry. The i can go where it was, so:

scanf("%d", &(A[i]->age));
scanf("%s", A[i]->name);

You still don't need to do this, however:

fuction(struct example *A[] ){

Just plain struct example *A is fine. A could be an array, just like char example *A could be (usually is) and int example *A could also point to either a single int or an array of them.