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C - Recursion C - Pointer Introduction C - Dereference Pointer (*)C - NULL Pointer C - Passing Pointers to Functions

C - Dereferencing a Pointer

Learn how to use the * operator to read or change the value stored at the address held by a pointer.

Reading a Value Using a Pointer

When a pointer stores the address of a variable, *ptr gives the value at that address. This is called dereferencing.

Example01

CCode Cell

1	#include <stdio.h>
2
3	int main()
4	{
5	int number = 10;
6	int *ptr = &number;
7
8	printf("number = %d\n", number);
9	printf("ptr = %d\n", ptr);
10
11	return 0;
12	}

Output

number = 10
*ptr = 10

Changing a Value Using a Pointer

You can assign a new value to *ptr. This changes the original variable because the pointer refers to its address.

Example02

CCode Cell

1	#include <stdio.h>
2
3	int main()
4	{
5	int number = 10;
6	int *ptr = &number;
7
8	printf("Before: %d\n", number);
9
10	*ptr = 50;
11
12	printf("After: %d\n", number);
13
14	return 0;
15	}

Output

Before: 10
After: 50

Remember the Difference

&number means the address of number.
ptr stores that address.
*ptr means the value at that address.

📝 Key Takeaways

The & operator gets an address.
The * operator accesses the value at a pointer address.
Changing *ptr can change the original variable.

🧠 Test Your Knowledge

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