Pointer declaration in C++ - Step-by-Step Execution

Concept Flow - Pointer declaration

Declare variable

↓

Declare pointer with *

↓

Pointer stores address of variable

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Use pointer to access variable

↓

End

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

Execution Sample

C++

int x = 10;
int* p = &x;
std::cout << *p;

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

Execution Table

Step	Action	Variable	Pointer	Value pointed by Pointer	Output
1	Declare int x = 10	x = 10	p = uninitialized	N/A	N/A
2	Declare pointer p to address of x	x = 10	p = &x (address)	10	N/A
3	Print value pointed by p (*p)	x = 10	p = &x	10	10
4	End of program	x = 10	p = &x	10	10

💡 Program ends after printing the value pointed by p.

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
x	undefined	10	10	10	10
p	undefined	undefined	&x (address)	&x (address)	&x (address)

Key Moments - 2 Insights

Why do we use * in int* p when declaring a pointer?

The * indicates that p is a pointer variable that will store the address of an int. See execution_table step 2 where p stores &x.

What does *p mean when printing *p?

*p means to access the value stored at the address p points to. In step 3, *p gives the value 10 stored in x.

Visual Quiz - 3 Questions

Look at the execution table, what is the value of p after step 2?

A The value 10

B Uninitialized

C The address of x

D Null pointer

💡 Hint

Check the 'Pointer' column in execution_table row for step 2.

At which step is the value pointed by p printed?

A Step 2

B Step 3

C Step 1

D Step 4

💡 Hint

Look at the 'Output' column in execution_table to find when 10 is printed.

If we change int* p = &x; to int* p = nullptr;, what will *p output?

A Undefined behavior or crash

B Address of x

C 10

D 0

💡 Hint

Refer to pointer initialization in variable_tracker and what happens when pointer is null.

Concept Snapshot

Pointer Declaration in C++:
- Use * to declare a pointer: int* p;
- Pointer stores address of a variable: p = &x;
- Access value via pointer: *p
- Pointer holds memory address, not value
- Dereferencing *p gives variable's value

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 and assigned the address of x using &x. The pointer p now holds the memory address of x. When we print *p, it accesses the value stored at that address, which is 10. The execution table traces these steps, showing variable and pointer states. Key points are that * in declaration means pointer type, and *p accesses the value pointed to. If p is null or uninitialized, dereferencing causes errors.