http://publib.boulder.ibm.com/infocenter/iseries/v5r3/topic/books/sc415721.pdf

Parts of a CL Procedure While each source statement entered as part of a CL procedure is actually a CL command, the source can be divided into the following basic parts used in many typical CL procedures. PGM command PGM PARM(&A) Optional PGM command beginning the procedure and identifying any parameters received. Declare commands (DCL, DCLF, COPYRIGHT) Mandatory declaration of procedure variables when variables are used. The declare commands must precede all other commands except the PGM command. CL processing commands CHGVAR, SNDPGMMSG, OVRDBF, DLTF, CL commands used as source statements to manipulate constants or variables (this is a partial list). Logic control commands IF, THEN, ELSE, DO, ENDDO, DOWHILE, DOUNTIL, DOFOR, LEAVE, ITERATE, GOTO, SELECT, ENDSELECT, WHEN, OTHERWISE Commands used to control processing within the CL procedure. Built-in functions %SUBSTRING (%SST), %SWITCH, and %BINARY (%BIN) Built-in functions and operators used in arithmetic, relational or logical expressions. Program control commands CALL, RETURN CL commands used to pass control to other programs. Procedure control commands CALLPRC, RETURN CL commands used to pass control to other procedures. ENDPGM command ENDPGM Optional End Program command.

Declaring a Variable In its simplest form, the Declare CL Variable (DCL) command has the following parameters: DCL &OBJ (TYPE) LEN(10)Specifying the Data TypeThe TYPE parameteron the DCL command also is required. This parameter specifies the type of data the variable can contain. CL supports six data types when declaring variables:*CHAR for variables containing character data

*LGL for variables containing logical data*DEC for variables containing numeric data in packed decimal format*INT for variables containing numeric data in signed integer format*UINT for variables containing numeric data in unsigned integer format*PTR for pointer variables containing a memory address

Unconditional branching means that you can instruct processing to branch to commands or sets of commands located anywhere in the procedure without regard to what conditions exist at the time the branch instruction is processed. Unconditional processing commands include:

GOTO

ITERATE

LEAVE

Conditional branching means that under certain specified conditions, processing may branch to sections or commands that are not consecutive within the procedure. The branching may be to any statement in the procedure. This is called conditional processing because the branching only occurs when the specified condition is true. Conditional processing is usually associated with the IF command. With the ELSE command, you can specify alternative processing if the condition is not true.The simple DO command allows you to create groups of commands that are always processed together, as a group, under specified conditions. Conditional processing commands include: v IF and THEN v SELECT, WHEN, and OTHERWISE v DOFOR v DOWHILE v DOUNTIL

IF COND(&OPTION=1) THEN(CALLPRC PRC(ADDREC)) ELSE CMD(IF COND(&OPTION=2) THEN(CALLPRC PRC(DSPFILE))) ELSE CMD(IF COND(&OPTION=3) THEN(CALLPRC PRC(PRINTFILE))) ELSE CMD(IF COND(&OPTION=4) THEN(CALLPRC PRC(DUMP))) RCLRSC RETURN

Up to 25 levels of such embedding are permitted in CL programming. As the levels of embedding increase and logic grows more complex, you may wish to enter the code in free-form design to clarify relationships: PGM DCL &A *DEC 1 DCL &B *CHAR 2 DCL &RESP *DEC 1 IF (&RESP=1) + IF (&A=5) + IF (&B=NO) THEN(DO) . . . ENDDO CHGVAR &A VALUE(8) CALL PGM(DAILY) ENDPGM

The following is an example of conditional processing with a DOUNTIL command. DOUNTIL (&LGL) . . . CHGVAR &INT (&INT + 1) IF (&INT *GT 5) (CHGVAR &LGL 1) ENDDO

The following is an example of conditional processing with a DOWHILE command. DOWHILE (&LGL) . . . IF (&INT *EQ 2) (CHGVAR &LGL 0) ENDDO

Using the ITERATE Command The ITERATE command can be used to skip the remaining commands in an active DOWHILE, DOUNTIL, or DOFOR group. ITERATE is not valid with simple DO command groups. An ITERATE command without a label will skip to the ENDDO of the innermost active DO group. Specifying a label skips to the ENDDO of the DO associated with the label. The following illustrates use of the ITERATE command: DO_1: DO_2:DOWHILE &LGL DO_3: DOFOR &INT FROM(0) TO(99) . . . IF (&A *EQ 12) THEN (ITERATE DO_1) . . /* Not processed if &A equals 12 */ . IF (&A *GT 12) ITERATE . . /* Not processed if &A greater than 12 */ . ENDDO . . . IF (&A *LT 0) (ITERATE DO_1) . . /* Not processed if &A less than zero */ . ENDDO

A LEAVE command without a label will leave the innermost active DO group. Specifying a label allows the processing to break out of one or more enclosing groups. The following illustrates use of the LEAVE command: DO_1: DO_2:DOWHILE &LGL DO_3: DOFOR &INT FROM(0) TO(99) . . . IF (&A *EQ 12) THEN(LEAVE DO_1) . . /* Not processed if &A equals 12 */ . IF (&A *GT 12) LEAVE . . /* Not processed if &A greater than 12 */ . ENDDO . . . IF (&A *LT 0) (LEAVE DO_1) . . /* Not processed if &A less than zero */ . ENDDO

The general structure of the SELECT command is as follows: SELECT WHEN (condition-1) THEN(command-1) . .WHEN (condition-n) THEN(command-n) OTHERWISE command-x ENDSELECT

SELECT WHEN (&LGL) WHEN (&INT *LT 0) THEN(CHGVAR &INT 0) WHEN (&INT *GT 0) (DOUNTIL (&INT *EQ 0)) CHGVAR &INT (&INT - 1) ENDDO OTHERWISE (CHGVAR &LGL 1) ENDSELECT