(define (startup)
  (display "data base file? (please enclose it in double quotes)")
  (let* ((db-file (open-input-file (read)))
         (descr-list (read db-file)) ; read the field descriptor list
         (all-records (read db-file)) ; read the records
         (new-db ; construct the updated data base
           (cond
             ((not (legal-descr-list? descr-list))
              (display '(*** bad field descriptor list ***))
              (newline)
              #f)
             ((not (legal-db? all-records descr-list))
              (display '(*** bad data base))
              (newline)
              #f)
             (else (process all-records all-records descr-list)) ) ) )
    (if new-db ; new-db = cons descr-list records
        (let ((new-db-file (open-output-file "db.out")))
          ; write the new field descriptor list (same as the old)
          (display (car new-db) new-db-file) 
          (newline new-db-file)
          ; write the new records
          (display "(" new-db-file)
          ; write each record on a separate line
          (map
            (lambda (record) (display record new-db-file) (newline))
            (cdr new-db) )
          (display ")" new-db-file)
          (newline)
          "thank you for using our data base") ) ) )

(define (legal-descr-list? L)
  (read) )

(define (legal-db? L1 L2)
  (read) )

(define (process working-data-base all-records descr-list)
  (display descr-list)
  (map (lambda (record) (display record) (newline)) working-data-base)
  (newline)
  (display 'command?)
  (let ((cmd (read)))
    (cond
      ((not (legal-cmd? cmd descr-list))
       (display '(*** bad command ***))
       (newline)
       (process working-data-base all-records descr-list))
      ((equal? (first cmd) 'reset)
       (process all-records all-records descr-list))
      ((equal? (first cmd) 'quit)
       (cons descr-list working-data-base))
      ((equal? (first cmd) 'sort)
       (process working-data-base all-records descr-list))
      ((equal? (first cmd) 'or)
       (process working-data-base all-records descr-list))
      (else
       (process working-data-base all-records descr-list) ) ) ) )

(trace legal-descr-list? legal-db? process)