after executing the printf statement, a recursive call must be made, so return and n, i, a, f are saved on s and the scratchpad values are set: n to n-1, a and i are interchanged, and the recursive call is made

case 1:

printf("\n %d -> %d\n",

i,f)

s_tack(2,n,i,a,f,&s);

setvar2(&n,&i,&a,&f);

goto one;