Question

Consider the following program. There are 11 statements in the program starting with int x; Show the memory allocated for the program in the stack and heap for each statement. Also, show any values assigned to each of these memory locations. In other words, you will show 11 stacks and 11 heaps as the answer to your question.

#include <iostream>

using namespace std;

int main() {

int x; // Stmt 1

int * y; // Stmt 2

y = new int; // Stmt 3

*y = 10; // Stmt 4

int * z; // Stmt 5

z = new int[5]; // Stmt 6

z[0] = 15; // Stmt 7

*(z + 1) = 20; // Stmt 8

delete y; // Stmt 9

y = z; // Stmt 10

delete [] z; // Stmt 11

return 0;

}

Answer 1

Note : New keyword is used to dynamically allocate memory in heap in C++, and delete keybord is used to free this memory from heap.

Lets see what happens for each statement :

int x; // Stmt 1

• This will create a integer variable in stack, having size equivalent to integer. This integer

will contain some garbage value.

int * y; // Stmt 2

• This will create a pointer variable in stack. This will contain NULL value as it has not assigned any value.

y = new int; // Stmt 3

• This will create a integer variable in heap and y will point to this heap memory section.

*y = 10; // Stmt 4

• This will assign value 10 to the integer space in the heap section, which was created in last section.

int * z; // Stmt 5

• This will create a pointer variable in stack. This will contain NULL value as it has not assigned any value.

z = new int[5]; // Stmt 6

• This will allocate memory in heap section equivalent to 5 integer in continuous form. z will point to first integer of this memory location.

z[0] = 15; // Stmt 7

• This will write 15 in index 0 of memory assigned in last step.

*(z + 1) = 20; // Stmt 8

• It will write 20 in index 1 of memory section, pointed by z.

delete y; // Stmt 9

• This will deallocate heap memory pointed by y.

y = z; // Stmt 10

• Now y will point to the same heap section, which is pointed by z pointer.Both will point to 1st integer of this heap section.

delete [] z; // Stmt 11

• This will deallocate(Free) heap memory pointed by z.

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