no form is in memory or if the data file is not open, an error message is displayed and control returns to the monitor. Data currently in memory will not be disturbed and will be displayed whenever the form is re-entered.
4.6 Revising an Existing Data File
4.6.1 The MOOIFYCommand
Any data record on a DF2 generated data file can be accessed for review or correction. The:
MOD [nn]
command enables the operator to manually access any data record created by a specified form and to then either bypass or change that record on the data file. The file is searched for the first data record created by the current form. Once a record has been found, the data file is in an "open" mode and may be searched in a forward direction by pressing the read next record function key (9), or, from the monitor mode, by entering another MOD command.
To access records already passed over, the rewind function key (7) rewinds the data file (as does the initial MOD command).
If the data file is in the ADD/START mode, the MOD command automatically writes an end of file mark on the data file.
During modification, a new form may be loaded (without disturbing the position of the data file) and that form will
subsequently be used for finding data records. Once a record has been found by the MOD command, the contents of all fields will be displayed in the form. Previously recorded data supercedes form constants, thus, the actual data from the file will be displayed, overlaying the form's constants (and changing its display, if different). However, the fOrm's constants will be set into the data record when the field is entered (as they are for new records) •
Data in a field may be changed at this time by entering new data in the field. Pressing ENTER in the first column of a field leaves the data unchanged. The edit criteria and field programs associated with the fields are still in effect~ and will be re-executed.
4.6.2 The FIND Command
If unique data in
the
record to be CorrecteQis
known, the:FIND [nn]
command may be used. This command loads the specified form (if different from the current form) and displays the form so the operator may enter characters into any fields to use as ~ key in
searching the file. All edit criteria are applied to fields
CHAPTER 4. THE INTERPRETER 4-5
(except field programs and required edit criteria) when setting up the match data.
\
When the data to be matc.hed has been entered, the operator must remernberto press the ENTER key after data has been entered in the last . field, of the search key· before pressing the read
record function key (9) to start the search •. The interpreter will search thedafa file forward looking for the record generated by the specified form and containing the specified data.
once the matching data has been found, operation proceeds as in the MOD commcmd.
I f a match is not found, the message:
END OF DATA
appears and control is returned to the interpreter~ s monitor.
The search may be terminated by preSSing both the KEYBOARD and DISPLAY keys simultaneously. The operator may·want to stop a
search if, for example, the wrong form is specified i or the wrong match data is given for a FIND. Control will be returned to the
interpreter's monitor •.. '
4.6.3 Rewriting Existing'Records
Data records are rewritten, in both FIND and MODIFY modes, by the use of the write record fUnction key (.). If the record was fetched using the MOD command, the next data record will
a utoma tically be read and di splayed. If the record was fetched by the FIND command, control is returned to the.interpreter's
monitor. ,
If no field needs to be changed, the next record can be fetched by pressing the read next record fUnction key (9); note that any modifications made will be destroyed by the read
function. The write record fUnction key (.) must be used to cause updating of the record (unless the write is executed by the field program, in which case the field assigned the program must be
entered). .
Records may be re-written up to 4 tiines. The configurator provides a command to reset the rewrite counters of a data file, so that more modifications may be made.
4.7 The BACKSPACE Command
In the ADD/START mode, the BACKSPACE
command backspaces the data file one logical record after writing an end of file mark on the data file and placing the data file in the MODIFY mode.
In the MODIFY mode, the BACKSPACE command back~paces twice and reads forward once under form number control; that is, if the record being read was not created by the current form, preceding records will be read until a form number match is found.
The backspace record fUnction key (8) also backspaces the data file.
4.8 The REWIND Command The:
REWIND
command rewinds the data file and positions to the first data recorq created by the form currently loaded.
If the data file is in the ADD/START mode, the REWIND command automatically writes an end of file mark on the data file.
The rewind fUnction key (7) also rewinds the data file.
4.9 The END Command The:
END
command writes an end of file mark on the data file. Switching from START/ADD mode to
MOOIF¥
modeaU'j:.Qfi,lat;icql).y
writesan
end of file mark on the data file. The ~ND command is rejected in the MODIFY mode.CHAPTER 4. THE INTERPRETER 4-7