1.
The Stack Segment is a segment that holds a stack. It's a stack implementation of memory locations. As the stack is a segment, it is a contiguous array of memory locations.The order in which elements come off a stack gives rise to its alternative name, LIFO (last in, first out). ... If the stack is full and does not contain enough space to accept an entity to be pushed, the stack is then considered to be in an overflow state. The pop operation removes an item from the top of the stack.
2.
The stack segment register (SS) is usually used to store information about the memory segment that stores the call stack of currently executed program. SP points to current stack top. ... To push a value to the stack, the PUSH instruction is used. To pop a value from the stack, the POP instruction is used.