For this field, enter the short hand code of a file, as define in option 1 of the main menu. When the program is run, the value input for the specified prompt definition is treated as the key to a record in the 'CHECK' file. The system will then the value entered by trying to read in a record with this value as a key to the 'CHECK' file. As a result of trying to read the record, the system variable RECORD.ON.FILE$ is set to true if the record is found and set to false if it is not found. In addition, if the record is not found, an error message will be output.

If D type variables are defined after the CHECK FILE prompt definition then these variables will be displayed off the 'CHECK' file record, should it be read in successfully.

A slight complication to the above situation is where the user is entering the 'CHECK' reference against the 'S' type prompt definition for the main file key. In normal cases, the user should enter the file reference entered at the top of the screen for the 'Update File Ref'. However, there are many occasions when the value entered needs to be validated against a secondary file before it can be accepted as the key, or part of the key, to the main update file. In such an instance, the user should enter the reference of the secondary file INSTEAD OF the main update file.

The system will generate code in the routine checking that the value entered is the key to a record on the secondary file. It will also create the key to the main update file and read the main record as well as.

As the system may access 2 separate files, it may be possible for 1 read to succeed but for the other to fail. Consequently, a different system variable is set to indicate the key to the main update file is valid. This variable is KEY.ON.FILE$. The variable RECORD.ON.FILE$ is set depending on the result of the read from the secondary file.

If the user does not know the reference of a required file then by hitting the invert key, the user will be transferred to the 'Files Used' screen, i.e. the screen linked to option 3. This will display the file references currently specified for the routine. If the file the user is interested in is not in this list, they can invoke the search utility by pressing the [INVERT] key. The user will then be asked for a part of the file name or part of the file reference. All those files that contain these values as part of the file name or reference will be displayed on the screen.

If the user then wishes to add one or more file references to the list of those already specified, they can do so now before returning back to the prompt definition screen. On returning back to the screen, the system will acknowledge any new references that have just been added.

Any Xref file specified in this field should be defined for use by the program via option 3 of the main menu. If a reference is specified for this entry and is not present in file list, the system displays the error message 'This has not been defined in the file list'. In addition the file must be created before you attempt to run your program, otherwise PARADYME will invoke the fatal runtime error routine.

A very useful feature of PARADYME is the ability to specify 'nested displays'. More details can be found here Nested Displays