HP 48gII - Manual (Page 772)

Page 26-3
Backup objects
Backup objects are used to copy data from your home directory into a
memory port. The purpose of backing up objects in memory port is to
preserve the contents of the objects for future usage. Backup objects have the
following characteristics:
• Backup objects can only exist in port memory (i.e., you cannot back
up an object in the HOME directory, although you can make as many
copies of it as you want)
• You cannot modify the contents of a backup object (you can, however,
copy it back to a directory in the HOME directory, modify it there,
and back it up again modified)
• You can store either a single object or an entire directory as a single
backup object. You cannot, however, create a backup object out of a
number of selected objects in a directory.
When you create a backup object in port memory, the calculator obtains a
cyclic redundancy check (CRC) or checksum value based on the binary data
contained in the object. This value is stored with the backup object, and is
used by the calculator to monitor the integrity of the backup object. When
you restore a backup object into the HOME directory, the calculator obtains
again the CRC value and compares it to the original value. If a discrepancy
is noticed, the calculator warns the user that the restored data may be
corrupted.
Backing up objects in port memory
The operation of backing up an object from user memory into one of the
memory ports is similar to the operation of copying a variable from one sub-
directory to another (see details in Chapter 2 of the User’s Guide). You can,
for example, use the File Manager (
„¡) to copy and delete backup
objects as you would do with normal calculator objects. In addition, there are
specific commands for manipulating back up objects, as described next.
Backing up and restoring HOME
You can back up the contents of the current HOME directory in a single back
up object. This object will contain all variables, key assignments, and alarms