CSCosmos - Computer Science Learning Hub

When a program runs, the Operating System gives it a block of memory. The program doesn't just use this block randomly; it organizes it into specific segments.

High Address

Stack

↓

Heap

↑

Data

Code (Text)

Low Address

Stack

LIFO (Last-In, First-Out)

Stores local variables and function call information. It grows and shrinks automatically.

Heap

Flexible size

Used for dynamic memory allocation. You (or your runtime) manage this space.

Data

Fixed size

Stores global and static variables that exist for the entire life of the program.

Code (Text)

Read-Only

The actual machine instructions of your program. Usually read-only.

Stack vs. Heap

The Stack is managed by the CPU and is extremely fast. Every time you call a function, a new "frame" is added to the stack. When the function returns, it's removed. The Heap is for larger, more complex data that needs to stay around longer.