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Double Pointers in C

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Introduction

A double pointer is a pointer that stores the address of another pointer.

👉 It is also called:

• Pointer to pointer
• Two-level pointer

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What is a Double Pointer?

A double pointer is:
👉 A pointer that points to another pointer

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Declaration of Double Pointer

data_type **pointer_name;

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Example

int **ptr;

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Initialization of Double Pointer

#include <stdio.h>

int main() {
    int a = 10;

    int *p = &a;
    int **dp = &p;

    printf("Value of a = %d\n", a);
    printf("Using pointer = %d\n", *p);
    printf("Using double pointer = %d\n", **dp);

    return 0;
}

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Output

Value of a = 10
Using pointer = 10
Using double pointer = 10

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Understanding Levels

Expression	Meaning
a	Value
&a	Address of a
p	Stores address of a
*p	Value of a
dp	Stores address of p
*dp	Address of a
**dp	Value of a

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Double Pointer Table (Styled)

Expression	Meaning
dp	Pointer to pointer
*dp	Pointer
**dp	Value

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Example: Changing Value Using Double Pointer

#include <stdio.h>

void change(int **ptr) {
    **ptr = 50;
}

int main() {
    int a = 10;
    int *p = &a;

    change(&p);

    printf("Value of a = %d", a);

    return 0;
}

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Output

Value of a = 50

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Real-World Uses

• Dynamic memory allocation
• Arrays of pointers
• Multi-level data structures
• Passing pointer to functions

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Important Notes

• Use correct number of *
• Initialize pointers properly
• Understand pointer levels

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Common Mistakes

• ❌ Confusing * and **
• ❌ Wrong declaration
• ❌ Uninitialized pointer
• ❌ Misunderstanding pointer levels

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Pro Tips

• ✔ Practice pointer levels
• ✔ Visualize memory
• ✔ Use simple examples first
• ✔ Combine with functions

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Conclusion

Double pointers are advanced but powerful concepts in C. They allow deeper control over memory and are useful in complex programs.

Master them to become strong in C programming.

👉 This article is part of Dharani Tech Edu Hub — where learning programming is made simple and practical.