Stack Frame

A stack frame, also known as an activation record, is a memory block on the call stack that is created when a function is called. It stores information related to the function call, such as:

• Local variables
• Function parameters
• Return address (where to return after the function finishes)
• Saved registers

When a function is called, a new stack frame is pushed onto the call stack. When the function returns, its stack frame is popped off the stack, and the program continues from the return address.

Example of stack frames during function calls:

1void function1() {
2  int x = 5;
3  function2();
4}
5
6void function2() {
7  int y = 10;
8  // ...
9}
10
11int main() {
12  function1();
13  // ...
14}

Stack frames during execution:

1. main() is called, creating a stack frame for main.
2. main() calls function1(), creating a new stack frame for function1.
3. function1() calls function2(), creating a new stack frame for function2.
4. When function2() returns, its stack frame is popped off the stack.
5. When function1() returns, its stack frame is popped off the stack.
6. When main() ends, its stack frame is popped off the stack.

Understanding stack frames is essential for grasping function calls, recursion, and the scope of local variables in C++.