Version 4.2.6 for Mainframes
 —  Programming Guide  —

Natural Programming Modes

This document describes the two programming modes offered by Natural. The following topics are covered:


Purpose of Programming Modes

Natural offers two ways of programming:

Note:
Generally, it is recommended to use structured mode exclusively, because it provides for more clearly structured applications.

Reporting Mode

Reporting mode is only useful for the creation of adhoc 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

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:

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 Functions in the Statements documentation.

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Setting/Changing the Programming Mode

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:

Structured Mode: GLOBALS SM=ON
Reporting Mode: 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.

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Functional Differences

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.

Syntax Related to Closing Loops and Functional Blocks

Reporting Mode:

(CLOSE) LOOP and DO ... DOEND statements are used for this purpose.

END-... statements (except END-DEFINE, END-DECIDE and END-SUBROUTINE) cannot be used.

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.

LOOP and DO/DOEND statements cannot be used.

The two examples below illustrate the differences between the two modes in constructing processing loops and logical conditions.

Reporting Mode Example:

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

Structured Mode Example:

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

Closing a Processing Loop in Reporting Mode

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.

Example 1 - LOOP:

FIND ... 
   FIND ... 
   ... 
   ... 
   LOOP      /* closes inner FIND loop 
LOOP         /* closes outer FIND loop 
... 
...

Example 2 - END:

FIND ... 
   FIND ... 
   ... 
   ... 
END             /* closes all loops and ends processing

Example 3 - SORT:

FIND ... 
   FIND ... 
   ... 
   ... 
SORT ...        /* closes all loops, initiates loop 
... 
END             /* closes SORT loop and ends processing

Closing a Processing Loop in Structured Mode

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.

Example 1 - FIND:

FIND ... 
   FIND ... 
   ... 
   ... 
   END-FIND       /* closes inner FIND loop 
END-FIND          /* closes outer FIND loop 
...

Example 2 - READ:

READ ... 
   AT END OF DATA 
   ... 
   END-ENDDATA 
   ... 
END-READ           /* closes READ loop 
... 
... 
END

Example 3 - SORT:

READ ... 
   FIND ... 
   ... 
   ... 
END-ALL         /* closes all loops 
SORT            /* opens loop 
... 
... 
END-SORT        /* closes SORT loop 
END

Location of Data Elements in a Program

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).

Database Reference

Reporting Mode:

In reporting mode, database fields and DDMs may be referenced without having been defined in a data area.

Structured Mode:

In structured mode, each database field to be used must be specified in a DEFINE DATA statement as described in Defining Fields and Accessing Data in an Adabas Database.

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