Sometimes programmers have a need to "save" the current values of fields and then restore then at some later time.

For instance a user may need to save the values of fields #A -> #C, and to do this you often code fields like this:

      define #sava reffld(#a)
      define #savb reffld(#b)
      define #savc reffld(#c)
and later .... (to save the values)
      change #sava #a
      change #savb #b
      change #savc #c
and still later .... (to restore the values)
 
      change #a #sava
      change #b #savb
      change #c #savc
 
An easier way to do this is to use a "working" list as a "stack" like this:

               def_list #stack (#a #b #c) type(*working) entrys(1)

to save the current values, "stack" them like this:

               inz_list #stack

to restore the values, "unstack" them like this:

               get_entry 1 #stack

Some other points about this technique are:

• You can have as many "stacks" as you like.
• The same field can be nominated in different stacks.
• The resulting code is probably more efficient than the original
• The stack can have more than 1 entry, allowing it to "stack" and "unstack" multiple different values. This is just like a true "stack" with "push" and "pull" facilities.