=====data Keyword 2=====
stack pop operation

====Definition====
  
Stack is a data structure that is used to keep things in order. A stack allows adding and removing items in order. When something is added to the stack it goes to the top of the stack, and the first item added to the stack is the last item to be removed.Pop is the operation used to remove an item from a stack.

====References====
List any sites, books, or sources utilized when researching information on this topic. (Remove any filler text).

  * Wikipedia
  * class
  * c book

=====data Keyword 2 Phase 2=====
stack underflow condition

====Definition====
When a command in a program tries to pop an element from an empty stack causing it to error out.

====References====

  * http://en.wikipedia.org/wiki/Stack_(abstract_data_type)
  * http://comjnl.oxfordjournals.org/content/20/1/56.full.pdf
====Demonstration====
Demonstration of the indicated keyword.

If you wish to aid your definition with a code sample, you can do so by using a wiki **code** block, an example follows:

<code c>

Stack A=NULL
</code>

Alternatively (or additionally), if you want to demonstrate something on the command-line, you can do so as follows:

<cli>
lab46:~$ ./stack
1. to pop
: 1
error stack underflow!
lab46:~$  
</cli>