Texas Instruments TI89 Developer Guide - Page 610

568 Appendix A: System Routines - Files FOpen (continued) Assumptions: (continued) When a file is opened with FOpen in FM_WRITE or FM_APPEND mode 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 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. 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 (continued) TI-89 / TI-92 Plus Developer Guide Not for Distribution Beta Version January 26, 2001