Stack stands for LIFO (Last in First Out).
So assuming a,9,e,,,,,_, a is at the bottom.
i).pop() //removes _
a,9,e,,_,,_,
ii).pop() //removes _
a,9,e,,_,,
iii).push(e) //adds e
a,9,e,,_,,e,
iv).push(1) adds 1
a,9,e,,_,,e,1,
v).pop()
a,9,e,,_,,e,
vi).push(i)
a,9,e,,_,,e,i,
vii).push(0)
a,9,e,,_,,e,i, (Not pushed as stack overflow)
viii).pop()
a,9,e,,_,,e,
ix).push(o)
a,9,e,,_,,e,o,
x).push(u)
a,9,e,,_,,e,i, (Not pushed as stack overflow)