100  DIM STACK$(1000)
110  DATA "(2*A)","PI","","TO BE OR","NOT TO BE"
120  FOR I = 1 TO 5
130  READ ELEMENT$
140  GOSUB 500_PUSH
150  NEXT
200  GOSUB 400 POP  AND  PRINT
210  GOSUB 300_EMPTY AND  PRINT
220  FOR I = 1 TO 4
230  GOSUB 400 POP  AND  PRINT
240  NEXT
250  GOSUB 300_EMPTY AND  PRINT
260  END
300  GOSUB 700_EMPTY
310  PRINT "STACK IS ";
320  IF  NOT EMPTY THEN  PRINT "NOT ";
330  PRINT "EMPTY"
340  RETURN
400  GOSUB 600 POP
410  PRINT ELEMENT$
420  RETURN
500  REM
510  REM PUSH
520  REM
530  LET STACK$(SP) = ELEMENT$
540  LET SP = SP + 1
550  RETURN
600  REM
610  REM POP
620  REM
630  IF SP THEN SP = SP - 1
640  LET ELEMENT$ = STACK$(SP)
650  LET STACK$(SP) = ""
660  RETURN
700  REM
710  REM EMPTY
720  REM
730  LET EMPTY = SP = 0
740  RETURN