What and Where are the Stack and Heap?

What is the Stack?

The stack is a region of memory used to store local variables and function parameters. It is a Last-In-First-Out (LIFO) data structure, meaning that the last item pushed onto the stack is the first item popped off the stack. The stack is managed and optimized by the CPU, making it very fast. When a function is called, the arguments to the function and the return address are pushed onto the stack. When the function returns, the return value is popped off the stack and the stack pointer is reset to the previous position.

What is the Heap?

The heap is a region of memory used to store dynamically allocated variables. It is a First-In-First-Out (FIFO) data structure, meaning that the first item allocated on the heap is the first item freed. The heap is managed by the operating system, making it slower than the stack. The heap is used to store variables that need to persist beyond the lifetime of the function that allocated them. For example, if a function allocates a large array, the array will be stored on the heap and a pointer to the array will be returned to the caller.

Where are the Stack and Heap?

The stack and heap are both located in the computer’s RAM. The stack is located at the bottom of the RAM and grows upwards. The heap is located at the top of the RAM and grows downwards. The two regions are separated by a guard page, which is a page of memory that is marked as inaccessible. This prevents the stack and heap from colliding with each other.

Code Examples

The following code example shows how to allocate a variable on the stack and on the heap:

// Allocate a variable on the stack
int x = 10;

// Allocate a variable on the heap
int *y = new int(10);

Conclusion

The stack and heap are two regions of memory used to store variables. The stack is used to store local variables and function parameters, while the heap is used to store dynamically allocated variables. The stack is managed and optimized by the CPU, making it faster than the heap, which is managed by the operating system. The stack and heap are located in the computer’s RAM, with the stack at the bottom and the heap at the top.