Stack vs. Heap Memory

When you run a program, the operating system assigns it some RAM. This memory is divided into two main areas: the Stack and the Heap.

The Stack (Ordered & Fast)

Think of a stack of plates. You can only add a plate to the top (Push), and you can only take a plate off the top (Pop). This is LIFO (Last In, First Out).

• What goes here? Local variables, function parameters, and return addresses.
• Speed: Extremely fast. The CPU just moves a pointer up or down.
• Limit: Small size (usually a few MB). If you exceed it (infinite recursion), you get a Stack Overflow.
• Automatic: Memory is freed immediately when a function finishes.

The Heap (Chaotic & Large)

Think of a giant laundry pile. You can throw clothes anywhere, and pull them out from anywhere.

• What goes here? Objects, Global variables, large data structures.
• Speed: Slower. The computer has to search for an empty spot to fit the data.
• Limit: Limited only by physical RAM (Gigabytes).
• Manual/GC: In languages like C++, you must delete this memory manually. In JavaScript/Python, a Garbage Collector scans the heap to clean up unused data, which causes performance pauses.

Summary

If you declare int x = 10;, it goes on the Stack.
If you declare User u = new User();, the pointer u is on the Stack, but the actual User object data is on the Heap.