Texas Instruments TI-89 Developer's Manual page 610

568
FOpen
(continued)
Assumptions: When a file is opened with FOpen in FM_WRITE or FM_APPEND mode
(continued) the associated variable is locked and inaccessible by any other routines in
the system. It must be closed with FClose to return the variable to not
in-use mode, to write the file type and the GEN_DATA_TAG, and to close
the associated buffer. For FILEs opened in FM_READ mode, the FClose
will merely update the mode of the file in the FILES structure to closed and
clear the associated error status.
There is no separate mode to open a file for both reading and writing.
However, if a file is opened in FM_APPEND mode the contents of the file
are not erased and the file may be subsequently positioned to any location
in the file (random access) and either read from or written to.
For all access modes the given name must not be a system variable. For
FM_READ/APPEND the name must be a third-party data-type. For
FM_WRITE the file must not exist or if it does it must be a third-party
data-type and the variable must not be locked or in-use.
Note that for files in READ mode FClose merely updates the
fsPtr ->fileMode field to indicate it is closed. For WRITE mode it must be
called to update information in the file needed by the system. While a file is
in WRITE mode it is marked as in-use so that no other application, or the
system, will try to access it (it will not be visible in the VAR-LINK screen
also). Files in WRITE or APPEND mode may be accessed randomly by
using FSetPos.
NOTE: Any number of files may be simultaneously opened in READ mode. If multiple
Side Effects: May cause heap compression or invalidate any current HSYMs.
Availability: On AMS 2.00 and higher.
TI-89 / TI-92 Plus
Differences: None
See Also: FAccess, FClose, FRead, FSetPos, FStatus, FWrite
TI-89 / TI-92 Plus Developer Guide
files are opened simultaneously in WRITE (or APPEND) mode than all but the
first file must already exist before they are opened. Use the FCreate routine if
they need to be created as empty files before they are opened with FOpen.
(continued)
Not for Distribution
Appendix A: System Routines — Files
Beta Version January 26, 2001