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C Pointers Mastery

bookPointer to Pointer

Sometimes you do not just want to change a value, you want to change it through another pointer. That is where a pointer to pointer comes in. Think of it like this:

  • int x holds a number;
  • int *p holds the address of x;
  • int **pp holds the address of p.

So the chain looks like:

pp → p → x → value

To reach the real value, you must dereference twice.

main.c

main.c

copy

              
12345678910111213141516

            
#include <stdio.h>

void set_to_ten(int **pp) {
    **pp = 10;
}

int main() {
    int x = 5;
    int *p = &x;
    int **pp = &p;

    set_to_ten(pp);

    printf("%d\n", x);  // prints 10
    return 0;
}

So basically you are setting the original variable x to 10 through two pointer levels. This is exactly what you need for the multi-level pointer task.

Note
Note

Pointer-to-pointer logic is most useful when a function must modify data that is already accessed through a pointer. If you forget one * when dereferencing, the program will compile but update the wrong level, so always double-check how many pointer layers you are working with.

question mark

What does dereferencing a pointer to pointer (*pp) return in the context where int x; int *p = &x; int **pp = &p;?

Select the correct answer

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bookPointer to Pointer

Pyyhkäise näyttääksesi valikon

Sometimes you do not just want to change a value, you want to change it through another pointer. That is where a pointer to pointer comes in. Think of it like this:

  • int x holds a number;
  • int *p holds the address of x;
  • int **pp holds the address of p.

So the chain looks like:

pp → p → x → value

To reach the real value, you must dereference twice.

main.c

main.c

copy

              
12345678910111213141516

            
#include <stdio.h>

void set_to_ten(int **pp) {
    **pp = 10;
}

int main() {
    int x = 5;
    int *p = &x;
    int **pp = &p;

    set_to_ten(pp);

    printf("%d\n", x);  // prints 10
    return 0;
}

So basically you are setting the original variable x to 10 through two pointer levels. This is exactly what you need for the multi-level pointer task.

Note
Note

Pointer-to-pointer logic is most useful when a function must modify data that is already accessed through a pointer. If you forget one * when dereferencing, the program will compile but update the wrong level, so always double-check how many pointer layers you are working with.

question mark

What does dereferencing a pointer to pointer (*pp) return in the context where int x; int *p = &x; int **pp = &p;?

Select the correct answer

Oliko kaikki selvää?

Miten voimme parantaa sitä?

Kiitos palautteestasi!

Osio 1. Luku 10
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