Editing Stack-oriented programming (section)

== Stack manipulation ==
Since the stack is the key means to manipulate data in a stack-oriented language, such languages often provide some sort of stack manipulation operators. Commonly provided are <code>dup</code>, to duplicate the element atop the stack, <code>exch</code> (or <code>swap</code>), to exchange elements atop the stack (the first becomes second and the second becomes first), <code>roll</code>, to cyclically permute elements in the stack or on part of the stack, <code>pop</code> (or <code>drop</code>), to discard the element atop the stack (push is implicit), and others. These become key in studying procedures.