Pointer declaration - Step-by-Step Execution

Concept Flow - Pointer declaration

Start

↓

Declare variable

↓

Declare pointer with *

↓

Pointer stores address of variable

↓

Use pointer to access variable

↓

End

This flow shows how a pointer is declared to store the address of a variable and then used to access that variable.

Execution Sample

C

int x = 10;
int *p = &x;
printf("Value via pointer: %d", *p);

Declare an integer x, declare a pointer p to int, assign p the address of x, then print the value pointed by p.

Execution Table

Step	Action	Variable	Pointer	Value Accessed	Output
1	Declare int x = 10	x=10	p=uninitialized	-	-
2	Declare pointer p to int	x=10	p=uninitialized	-	-
3	Assign p = &x (address of x)	x=10	p=&x	-	-
4	Access value via *p	x=10	p=&x	10	Value via pointer: 10

💡 Program ends after printing value accessed through pointer *p.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	After Step 4
x	undefined	10	10	10	10
p	undefined	undefined	undefined	&x	&x

Key Moments - 3 Insights

Why do we use * in the pointer declaration?

The * tells the compiler that p is a pointer to an int, not an int itself. See execution_table step 2 where p is declared as a pointer.

What does &x mean in the assignment to p?

&x means the address of variable x. In step 3, p stores this address, so p points to x.

How does *p give the value of x?

*p means 'the value at the address stored in p'. Since p points to x, *p accesses x's value, shown in step 4.

Visual Quiz - 3 Questions

Look at the execution_table at step 3, what does p hold?

A The value 10

B The address of x

C Undefined

D The value of *p

💡 Hint

Check the 'Pointer' column at step 3 in the execution_table.

At which step is the value 10 accessed through the pointer?

A Step 4

B Step 1

C Step 3

D Step 2

💡 Hint

Look at the 'Value Accessed' and 'Output' columns in the execution_table.

If we change int *p = &x; to int *p = NULL;, what would *p access?

A Value 10

B Address of x

C Undefined or error

D Value 0

💡 Hint

Refer to pointer initialization and what happens if pointer does not point to a valid address.

Concept Snapshot

Pointer declaration in C:
int *p; declares p as a pointer to int.
Use & to get variable address: p = &x;
Use *p to access value at that address.
Pointers store addresses, not values.
Dereferencing *p accesses the variable pointed to.

Full Transcript

This example shows how to declare a pointer in C. First, an integer variable x is declared and set to 10. Then, a pointer p is declared with int *p, meaning p will hold the address of an int. Next, p is assigned the address of x using &x. Finally, the value of x is accessed by dereferencing p with *p, which prints 10. The execution table traces each step, showing variable and pointer states. Key points include understanding that * in declaration means pointer type, & gets address, and *p accesses the value at that address.