homogeneous array : a rectangular block of data whose entries are of the sme type.
heterogeneous array:a block of data items that be of different type.
The beginning of a list is called the head of the list.
The other end of a list is called the tail.
A stack is a list in which entries are removed and inserted only at the head.
The head of a stack is called the top of the stack.
The tail of a stack is called the bottom or base.