new operator in C++ - Step-by-Step Execution

Concept Flow - new operator

Program starts

↓

Call new operator

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Allocate memory on heap

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Return pointer to memory

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Use pointer to access memory

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Delete pointer to free memory

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Program ends

The new operator allocates memory on the heap and returns a pointer to it, which you can use until you delete it to free memory.

Execution Sample

C++

int* p = new int(10);
std::cout << *p << std::endl;
delete p;

This code allocates an int with value 10 on the heap, prints it, then frees the memory.

Execution Table

Step	Action	Memory Allocation	Pointer Value	Output
1	Call new int(10)	Allocates int with value 10 on heap	Pointer p points to new int
2	Dereference pointer *p	No new allocation	Pointer p unchanged	10
3	Delete pointer p	Memory freed	Pointer p becomes dangling (not safe to use)
4	End program	No allocation	Pointer p is dangling

💡 Program ends after memory is freed with delete

Variable Tracker

Variable	Start	After Step 1	After Step 2	After Step 3	Final
p	uninitialized	points to heap int(10)	points to heap int(10)	dangling pointer	dangling pointer

Key Moments - 3 Insights

Why do we need to use delete after new?

Because new allocates memory on the heap that stays until deleted. Without delete, memory stays allocated causing leaks (see step 3 in execution_table).

What happens if we try to use pointer p after delete?

Pointer p becomes dangling after delete (step 3). Using it after delete can cause errors or crashes.

Does new initialize the allocated memory?

Yes, in this example new int(10) initializes the int to 10 (step 1). Without (10), the value would be undefined.

Visual Quiz - 3 Questions

Look at the execution_table, what is the output at step 2?

A 10

B Pointer address

C Undefined

D 0

💡 Hint

Check the Output column at step 2 in execution_table

At which step does the pointer become unsafe to use?

A Step 1

B Step 3

C Step 2

D Step 4

💡 Hint

Look at the Pointer Value column in execution_table for step 3

If we omit delete, what changes in the execution_table?

A Memory is freed automatically

B Program crashes immediately

C Memory is never freed, pointer stays valid

D Pointer becomes dangling earlier

💡 Hint

Refer to the Memory Allocation and Pointer Value columns in execution_table

Concept Snapshot

new operator allocates memory on the heap and returns a pointer.
Use new Type(value) to create and initialize.
Always pair new with delete to free memory.
Pointer holds address of allocated memory.
Dereference pointer to access value.
Using pointer after delete is unsafe.

Full Transcript

The new operator in C++ allocates memory on the heap and returns a pointer to that memory. For example, int* p = new int(10); creates an integer with value 10 on the heap and p points to it. You can access the value by dereferencing p with *p. After using the memory, you must call delete p; to free it. If you don't delete, the memory stays allocated causing a memory leak. After delete, the pointer becomes dangling and should not be used. This trace shows each step: allocation, access, deletion, and program end.