The Art of Assembly Language, 2nd Edition

3.9 The Stack Is a LIFO Data Structure

You can push more than one value onto the stack without first popping previous values off the stack. However, the stack is a last-in, first-out (LIFO) data structure, so you must be careful how you push and pop multiple values. For example, suppose you want to preserve EAX and EBX across some block of instructions; the following code demonstrates the obvious way to handle this:

push( eax );
          push( ebx );
          << Code that uses eax and ebx goes here. >>
          pop( eax );
          pop( ebx );

Unfortunately, this code will not work properly! Figure 3-13 through Figure 3-16 show the problem. Because this code pushes EAX first and EBX second, the stack pointer is left pointing at EBX's value on the stack. When the pop( eax ); instruction ...