Pointer Initialization

I was having a lecture about pointers and I thought I understood already. Until I tried this simple code that doesn't work. It gives "Segmentation fault: 11".

Code:

---

#include<stdio.h>

int main()
{
  int *a;
    scanf("%d", a);
    printf("%d", *a);
    return 0;
}

---

This is my understanding: in the initialization int *a, I set a to be an address pointing to an integer. Then I scan an integer and store it on the address of a. Finally I print the integer stored in the address of a. So, what went wrong?

Quote:

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Originally Posted by johan.g1

I was having a lecture about pointers and I thought I understood already. Until I tried this simple code that doesn't work. It gives "Segmentation fault: 11".

Code:

---

#include<stdio.h>

int main()
{
  int *a;
    scanf("%d", a);
    printf("%d", *a);
    return 0;
}

---

This is my understanding: in the initialization int *a, I set a to be an address pointing to an integer. Then I scan an integer and store it on the address of a. Finally I print the integer stored in the address of a. So, what went wrong?

---

'a' is a pointer, but it doesn't point to anywhere yet

Give it somewhere to point to first

Code:

---

#include<stdio.h>


int main()
{
    int b;
    int *a;

    a = &b;


    scanf("%d", a);
    printf("%d", *a);
    return 0;
}

---

A better example would be the following:

By better I am not saying better than Click_here's example, I am referring to the original poster's example.

Code:

---

#include <stdio.h>

int main(){
    int a = 0;
    int * b = &a;

    *b = 5;
    printf("%d", a);

    return 0;
}

---

This uses pointers to change the variable 'a' to 5 without directly using it.

Quote:

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Originally Posted by Khaltazar

A better example would be the following:
This uses pointers to change the variable 'a' to 5 without directly using it.

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Aside from a and b being renamed, Click_here's didn't directly use the pointee either. The pointee being the thing that a pointer points to, I mean.

Quote:

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Originally Posted by whiteflags

Aside from a and b being renamed, Click_here's didn't directly use the pointee either. The pointee being the thing that a pointer points to, I mean.

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I didn't mean it was better than the poster above me, I was replying to the original poster. I usually don't use quotes unless I am replying to someone other than the original poster.

My code was not an example - It was just a slight change to the OP's code to make it work.

Thanks. I think I got it now. :D