How Recursion uses stack

In C++, recursion utilizes the stack for managing function calls and storing local variables. Here's a breakdown of how this works:

• Activation Records: Each time a function is called, an activation record (or stack frame) is created for that specific call. This record contains information about the function, including its local variables and the return address.

• Stack Growth: As recursive calls are made, more activation records are added to the stack. For instance, if a function calls itself four times, there will be four separate activation records in place. This can only happen until the base case of the recursion is reached.

• Memory Consumption: Because each recursive call allocates memory for its activation record on the stack, deep recursion can lead to high memory consumption. The total memory required will depend on the number of recursive calls made.

• Return Process: Once the base case is hit, the function begins returning, and the activation records are popped off the stack one by one. Each time an activation frame is removed, it frees up the memory that was used for that specific call.

• Stack Overflow: If the recursion is too deep—theoretically beyond the size limit of the stack—this can lead to a stack overflow, which will terminate the program.

In summary, C++ recursion heavily relies on the stack to manage simultaneously executing function calls and local variable storage. Each function call increases stack usage, and memory is released when those calls finish. This is why recursive functions can be memory-intensive.