PA0465 Console Scientific Calculator Program

                                                          
  Expression file operations are controlled from a window 
  entered by interrupting under 'Expression files' on     
  line 4.                                                 
  When a save is made the calculation lines (line number 7
  and line number 9) are saved into a file exactly as they
  are at the time. This allows you to type in descriptive 
  variable names in place of actual values. A user-entered
  title is saved with the file. A restore simply replaces 
  whatever is on lines 7 and 9 with the data stored in the
  file.