This document describes the two programming modes offered by Natural.
Note
Generally, it is recommended to use structured mode exclusively, because it provides
for more clearly structured applications. Therefore, the explanations and examples in the
Programming Guide usually refer to structured mode only.
The following topics are covered:
Natural offers two ways of programming:
Reporting mode is only useful for the creation of ad hoc reports and small programs which do not involve complex data and/or programming constructs. (If you decide to write a program in reporting mode, be aware that small programs may easily become larger and more complex.)
Please note that certain Natural statements are available only in reporting mode, whereas others have a specific structure when used in reporting mode. For an overview of the statements that can be used in reporting mode, see Reporting Mode Statements in the Statements documentation.
Structured mode is intended for the implementation of complex applications with a clear and well-defined program structure. The major benefits of structured mode are:
The programs have to be written in a more structured way and are therefore easier to read and consequently easier to maintain.
As all fields to be used in a program have to be defined in one central location (instead of being scattered all over the program, as is possible in reporting mode), overall control of the data used is much easier.
With structured mode, you also have to make more detail planning before the actual programs can be coded, thereby avoiding many programming errors and inefficiencies.
For an overview of the statements that can be used in structured mode, see Statements Grouped by Function in the Statements documentation.
The default programming mode is set by the Natural administrator with the profile
parameter SM.
You can change the mode by using the Natural system command GLOBALS and the session parameter SM:
| Mode | System Command |
|---|---|
| Structured | GLOBALS SM=ON |
| Reporting | GLOBALS SM=OFF |
For further information on the Natural profile and session parameter
SM, see SM - Programming
in Structured Mode in the Parameter
Reference.
For information on how to change the programming mode, see Programming Modes in Using Natural and SM - Programming in Structured Mode in the Parameter Reference.
The following major functional differences exist between reporting mode and structured mode:
Note
For detailed information on functional differences that exist between the two modes,
see the Statements
documentation. It provides separate syntax diagrams and syntax element descriptions for
each mode-sensitive statement. For a functional overview of the statements that can be
used in reporting mode, see Reporting Mode Statements in the
Statements documentation.
| Reporting Mode: |
(CLOSE) LOOP and
DO ... DOEND
statements are used for this purpose.
|
|---|---|
| Structured Mode: | Every loop or logical construct must be explicitly closed
with a corresponding END-... statement. Thus, it becomes
immediately clear, which loop/logical constructs ends where.
|
The two examples below illustrate the differences between the two modes in constructing processing loops and logical conditions.
The reporting mode example uses the statements DO and DOEND to mark the beginning and end of
the statement block that is based on the AT END
OF DATA condition. The END statement closes all active processing loops.
READ EMPLOYEES BY PERSONNEL-ID
DISPLAY NAME BIRTH
AT END OF DATA
DO
SKIP 2
WRITE / 'LAST SELECTED:' OLD(NAME)
DOEND
END
The structured mode example uses an END-ENDDATA statement to close the
AT END OF DATA condition,
and an END-READ statement to close the READ loop. The result is a more clearly structured program
in which you can see immediately where each construct begins and ends:
DEFINE DATA LOCAL
1 MYVIEW VIEW OF EMPLOYEES
2 PERSONNEL-ID
2 NAME
2 BIRTH
END-DEFINE
READ MYVIEW BY PERSONNEL-ID
DISPLAY NAME BIRTH
AT END OF DATA
SKIP 2
WRITE / 'LAST SELECTED:' OLD(NAME)
END-ENDDATA
END-READ
END
The statements END, LOOP (or CLOSE LOOP) or
SORT may be used to close a
processing loop.
The LOOP statement can be used to close more than one loop, and the
END statement can be used to close all active loops. These possibilities
of closing several loops with a single statement constitute a basic difference to
structured mode.
A SORT statement closes all processing loops and initiates another
processing loop.
FIND ... FIND ... ... ... LOOP /* closes inner FIND loop LOOP /* closes outer FIND loop ... ...
FIND ... FIND ... ... ... END /* closes all loops and ends processing
FIND ... FIND ... ... ... SORT ... /* closes all loops, initiates loop ... END /* closes SORT loop and ends processing
Structured mode uses a specific loop-closing statement for each processing loop. Also,
the END statement does not close
any processing loop. The SORT
statement must be preceded by an END-ALL statement, and the
SORT loop must be closed with an END-SORT statement.
FIND ... FIND ... ... ... END-FIND /* closes inner FIND loop END-FIND /* closes outer FIND loop ...
READ ... AT END OF DATA ... END-ENDDATA ... END-READ /* closes READ loop ... ... END
READ ... FIND ... ... ... END-ALL /* closes all loops SORT /* opens loop ... ... END-SORT /* closes SORT loop END
In reporting mode, you can use database fields without having to define them in a
DEFINE DATA statement;
also, you can define user-defined variables anywhere in a program, which means that they
can be scattered all over the program.
In structured mode, all data elements to be used have to be defined in one
central location (either in the DEFINE DATA statement at the beginning of
the program, or in a data area outside the program).
In reporting mode, database fields and data definition modules (DDMs) may be referenced without having been defined in a data area.
In structured mode, each database field to be used must be specified in a DEFINE DATA statement as described in
Field Definitions and
Database
Access.
