Stack Allocation

When we create new variables, they go on the stack.

Abstractly, the stack is populated with items that we maintain or own, such as variables, or function calls.

Let's say we allocate a few variables in the C code below.

int main() {
    int x = 5;
  int y = 10;

  int arr[3] = {1,2,3};
}

A simple mental model might look something like this:

• Our variable x has a value of 5, which is located somewhere in the stack.

• Our variable y has a value of 10, which is located somewhere in the stack.

• Our variable arr has 3 elements, 1,2,3, which are located somewhere in the stack.

Heap Allocation

The heap houses items that are not under our direct control.

We can directly put items on the heap and point to them.

Below, the variable x is on the stack, pointing to the value 5 on the heap.

int main() {
    int *x = 5;
}