Structured Programming Operations

The structured programming operations are shown in the following table.

Table 1. Structured Programming Operations
Operation	Traditional Syntax	Free-Form Syntax
And	ANDxx (And)	AND operator
Do	DO (Do)	FOR (For)
Do Until	DOU (Do Until) or DOUxx (Do Until)	DOU (Do Until)
Do While	DOW (Do While) or DOWxx (Do While)	DOW (Do While)
Else	ELSE (Else)	ELSE (Else)
Else If	ELSEIF (Else If)	ELSEIF (Else If)
End	ENDyy (End a Structured Group)	ENDyy (End a Structured Group)
For	FOR (For)	FOR (For)
For-Each	FOR-EACH (For Each)	FOR-EACH (For Each)
If	IF (If) or IFxx (If)	IF (If)
Iterate	ITER (Iterate)	ITER (Iterate)
Leave	LEAVE (Leave a Do/For Group)	LEAVE (Leave a Do/For Group)
Or	ORxx (Or)	OR operator
Otherwise	OTHER (Otherwise Select)	OTHER (Otherwise Select)
Select	SELECT (Begin a Select Group)	SELECT (Begin a Select Group)
When	WHEN (When True Then Select) or WHENxx (When True Then Select)	WHEN (When True Then Select)

The DO operation allows the processing of a group of calculations zero or more times starting with the value in factor 1, incrementing each time by a value on the associated ENDDO operation until the limit specified in factor 2 is reached.

The DOU and DOUxx (Do Until) operations allow the processing of a group of calculations one or more times. The end of a Do-Until operation is indicated by an ENDDO operation.

The DOW and DOWxx (Do While) operations allow the processing of a group of calculations zero or more times. The end of a Do-While operation is indicated by an ENDDO operation.

The FOR operation allows the repetitive processing of a group of calculations. A starting value is assigned to the index name. Increment and limit values can be specified, as well. Starting, increment, and limit values can be free-form expressions. An ENDFOR operation indicates the end of the FOR group.

The FOR-EACH operation allows each item in an array or %LIST to be processed one at a time. An ENDFOR operation indicates the end of the FOR-EACH group.

The LEAVE operation interrupts control flow prematurely and transfers control to the statement following the ENDDO or ENDFOR operation of an iterative structured group. The ITER operation causes the next loop iteration to occur immediately.

The IF and IFxx operations allow the processing of a group of calculations if a specified condition is satisfied. The ELSE operation allows you to specify a group of calculations to be processed if the condition is not satisfied. The ELSEIF operation is a combination of an ELSE operation and an IF operation. The end of an IF or IFxx group is indicated by ENDIF.

The SELECT, WHEN, WHENxx, and OTHER group of operations are used to conditionally process one of several alternative sequences of operations. The beginning of the select group is indicated by the SELECT operation. The WHEN and WHENxx operations are used to choose the operation sequence to process. The OTHER operation is used to indicate an operation sequence that is processed when none of the WHENxx conditions are fulfilled. The end of the select group is indicated by the ENDSL operation.

The ANDxx and ORxx operations are used with the DOUxx, DOWxx, WHENxx, and IFxx operations to specify a more complex condition. The ANDxx operation has higher precedence than the ORxx operation. Note, however, that the IF, DOU, DOW, and WHEN operations allow a more straightforward coding of complex expressions than their xx counterparts.

Figure 1. Example of AND/OR Precedence

*...1....+....2....+....3....+....4....+....5....+....6....+....7...
CL0N01Factor1+++++++Opcode(E)+Factor2+++++++Result++++++++Len++D+HiLoEq....
 *
 * In the following example, indicator 25 will be set on only if the
 * first two conditions are true or the third condition is true.
 *
 * As an expression, this would be written:
 * EVAL *IN25 = ((FIELDA > FIELDB) AND (FIELDA >= FIELDC)) OR (FIELDA < FIELDD)
 *
 *
C     FIELDA        IFGT      FIELDB
C     FIELDA        ANDGE     FIELDC
C     FIELDA        ORLT      FIELDD
C                   SETON                                        25
C                   ELSE
C                   SETOFF                                       25
C                   ENDIF

A DO, DOUxx, DOWxx, FOR, IFxx, MONITOR, or SELECT operation (with or without ANDxx or ORxx operations), and an ENDyy operation, delimit a structured group. The ENDDO operation ends each DO, DOUxx, and DOWxx group or causes the structured group to be reprocessed until the specified ending conditions are met. The ENDFOR operation ends each FOR group. The SELECT must end with an ENDSL. An IFxx operation and an IFxx operation with an ELSE operation must end with an ENDIF operation.

The rules for making the comparison on the ANDxx, DOUxx, DOWxx, IFxx, ORxx and WHENxx operation codes are the same as those given under Compare Operations.

In the ANDxx, DOUxx, DOWxx, IFxx, ORxx, and WHENxx operations, xx can be:

xx: Meaning
GT: Factor 1 is greater than factor 2.
LT: Factor 1 is less than factor 2.
EQ: Factor 1 is equal to factor 2.
NE: Factor 1 is not equal to factor 2.
GE: Factor 1 is greater than or equal to factor 2.
LE: Factor 1 is less than or equal to factor 2.

In the ENDyy operation, yy can be:

yy: Meaning
CS: End for CASxx operation.
DO: End for DO, DOUxx, and DOWxx operation.
FOR: End for FOR operation.
IF: End for IFxx operation.
SL: End for SELECT operation.
Blanks: End for any structured operation.

Note: The yy in the ENDyy operation is optional.

If a structured group, in this case a do group, contains another complete structured group, together they form a nested structured group. Structured groups can be nested to a maximum depth of 100 levels. The following is an example of nested structured groups, three levels deep:

REQTEXT — Figure 2. Nested Structured Groups

Remember the following when specifying structured groups:

Each nested structured group must be completely contained within the outer level structured group.
Each structured group must contain one of a DO, DOUxx, DOWxx, FOR, FOR-EACH, IFxx, or SELECT operation and its associated ENDyy operation.
A structured group can be contained in detail, total, or subroutine calculations, but it cannot be split among them.
Branching into a structured group from outside the structured group may cause undesirable results.