How are variables stored in memory in recursion?

Question

I'm unsure about how variables are created and stored in memory during recursion. Below is an example taken from C Primer Plus:

#include <stdio.h>
void recursiontest(int); 

int main(){
    recursiontest(3); 
    return 0; 
}


void recursiontest(int n){
    printf("Level %d : %#x\n", n, &n); 
    if(n < 4)
        recursiontest(n + 1); 
    printf("LEVEL %d : %#x\n", n, &n);
    return;  
}

Which yields the output:

Level 3 : 0x3ce1f8bc

Level 4 : 0x3ce1f89c

LEVEL 4 : 0x3ce1f89c

LEVEL 3 : 0x3ce1f8bc

It appears as though the "n" variable local to the original function call is of an address sequentially later than that of the first (and only) recursive call. Why is that?

When I call a function, aren't its formal parameters declared and defined in terms of the actual argument passed to it? Wouldn't that mean that the integer n local to the first call is created before the second (recursive) call? How could the n of the second call have an address earlier than the first call?

Answer 1

This is because the local automatic variables created during the recursive function calls are stored on the stack, and the stack grows "down" from a higher to lower address on most platforms, including x86. Thus a function that is called later in the process will have variables with a "lower" address than variables stored from an earlier function call.