Pointers – Understanding Memory Addresses

UpdatedMarch 2, 2026

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C Programming

Part 20 of 40

From today, I will be starting lessons on C programming in my ALX Software Engineering class and I look forward to sharing with you everything I learn through this series.

Up next

Arrays and Pointers – Understanding Their Relationship

In the last lesson, we learned: What pointers are How & gives an address How * dereferences a pointer Now we connect that knowledge to arrays. This is the moment many students say: “Ohhhh… so th

1. What Is Memory?

When you write:

int n = 98;

The computer:

Finds a location in memory
Stores the value 98 there
Gives that location an address

Every variable has:

A value
An address

You normally work with the value.

Pointers let you work with the address.

2. Getting the Address of a Variable

To get the address of a variable, use the & operator.

Example:

#include <stdio.h>

int main() {
    int n = 98;
    printf("Value of n: %d\n", n);
    printf("Address of n: %p\n", &n);
    return 0;
}

&n means:

“Give me the address of n.”

%p is used to print memory addresses.

You will see something like:

0x7ffd3c4b8a1c

That is the memory location.

3. What Is a Pointer?

A pointer is:

A variable that stores the address of another variable.

It does not store the value directly.

It stores where the value lives.

4. Declaring a Pointer

To declare a pointer:

data_type *pointer_name;

Example:

int *p;

This means:

p is a pointer
It will store the address of an integer

Important:

The type matters.

If you write:

int *p;

Then p must point to an int.

5. Storing an Address in a Pointer

Example:

int n = 98;
int *p = &n;

What happens here?

n stores 98.
&n gives the address of n.
p stores that address.

So now:

p → address of n

6. Dereferencing a Pointer

The * operator has two meanings:

In declaration:

int *p;

It means “p is a pointer”.

In usage:

*p

It means:

“Go to the address stored in p and get the value.”

Example:

#include <stdio.h>

int main() {
    int n = 98;
    int *p = &n;

    printf("Value of n: %d\n", n);
    printf("Value using pointer: %d\n", *p);

    return 0;
}

*p gives you 98.

Because:

p stores the address of n
*p goes to that address
It retrieves the value stored there

7. Modifying a Value Using a Pointer

Here’s where it gets powerful.

#include <stdio.h>

int main() {
    int n = 98;
    int *p = &n;

    *p = 402;

    printf("n = %d\n", n);
    return 0;
}

What happens?

p points to n
*p = 402 changes the value at that address
Since that address belongs to n, n becomes 402

So pointers allow you to modify the original variable.

8. Visual Memory Example

Imagine memory like this:

Address: 1000
Value:   98

Now:

n → 1000
p → 1000

When you write:

*p = 402;

You are changing:

Value at address 1000

So n changes.

9. Why Pointers Matter

Pointers are used for:

Working with arrays
Strings
Dynamic memory
Passing variables to functions by reference
Building data structures

Without pointers, C would not be powerful.

10. Common Beginner Mistakes

❌ Using a pointer without initializing it

int *p;
*p = 10;   // Dangerous!

This causes undefined behavior.

Always assign an address before dereferencing.

❌ Confusing `&` and `*`

& → Get address
* → Go to address

❌ Forgetting pointer type must match variable type

float f = 3.14;
int *p = &f;  // Wrong

Types must match.

11. Practice Exercises

Create an integer variable and print its address.
Create a pointer that stores the address of that variable.
Use the pointer to change the variable’s value.
Draw the memory state on paper.

Try this:

int n;
int *p;
n = 98;
p = &n;
*p = 402;

Question:

What is the final value of n?
Why?

Final Thoughts

Today you learned:

Every variable has an address.
& gives the address.
A pointer stores that address.
*p accesses the value at that address.
Changing *p changes the original variable.

Pointers are not magic.

They are simply variables that store memory addresses.

In the next lesson, we will connect pointers and arrays.

And that’s when things really start making sense.

Pointers – Understanding Memory Addresses

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Arrays and Pointers – Understanding Their Relationship

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1. What Is Memory?

2. Getting the Address of a Variable

3. What Is a Pointer?

4. Declaring a Pointer

5. Storing an Address in a Pointer

6. Dereferencing a Pointer

7. Modifying a Value Using a Pointer

8. Visual Memory Example

9. Why Pointers Matter

10. Common Beginner Mistakes

❌ Using a pointer without initializing it

❌ Confusing `&` and `*`

❌ Forgetting pointer type must match variable type

11. Practice Exercises

Final Thoughts

Command Palette

Comments

C Programming

Arrays and Pointers – Understanding Their Relationship

More from this blog

1. What Is Memory?

2. Getting the Address of a Variable

3. What Is a Pointer?

4. Declaring a Pointer

5. Storing an Address in a Pointer

6. Dereferencing a Pointer

7. Modifying a Value Using a Pointer

8. Visual Memory Example

9. Why Pointers Matter

10. Common Beginner Mistakes

❌ Using a pointer without initializing it

❌ Confusing & and *

❌ Forgetting pointer type must match variable type

11. Practice Exercises

Final Thoughts

❌ Confusing `&` and `*`