Operational Control Language

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Operational Control Language (OCL) is the control language of the IBM System/34 and System/36 minicomputer family. Other control languages include CL (System/38 and AS/400), JCL (System/370), and REXX (AS/400). The facility of DOS to use batch files is also control language.

On the IBM S/34 and S/36, OCL statements are used to directly load user or system programs into memory, assign system resources to them, and transfer system control to them in a process called execution. The fact that a program is on a computer's disk drive does not in itself cause the computer to begin working on the program.

OCL statements can be entered from the keyboard, but are generally stored in a S/34-S/36 procedure member. A procedure member is a freely editable member within a library, not dissimilar from a source member. On the S/34-S/36, procedures are not compiled.

OCL statements begin with two slashes and a space. Here's an example of a short procedure stored on a System/36 as PROC1:

 ** Procedure PROC1
 ** Written by Joe User 2006-05-29
 // * 'PROC1 procedure is running'
 // * ' '
 ** IFF means 'if false'
 ** ACTIVE-'nnn,nnn2' means at least one of the listed programs is currently running
 ** GOTO xxx means skip to the statement that says TAG xxx and resume processing
 // PAUSE ' Cannot continue because other Payroll is running'
 // CANCEL                                               stops execution of this procedure
 // * ' Caution, Pay Data Exists'                        displays info on CRT
 // * ' '
 // * ' Press 1 to continue and DELETE existing files'
 // IFF '1'=?1R? CANCEL     A parameter is indicated by question marks surrounding a number
 ** Using 1R between question marks indicates that the parameter is required and processing
 ** waits for user input.  CANCEL means immediately go to end of job.
 // LOAD $DELET                                         $DELET is used to delete files
 // RUN
 // IF DATAF1-PFILE1 SCRATCH UNIT-F1,LABEL-PFILE1       deletes a disk file
 // END                                              END returns control from a system program
 // LOAD PR101                                          PR101 is the sample RPG program
 // FILE NAME-PAYMAST,DISP-SHR                          PAYMAST is the payroll master file
 // FILE NAME-PFILE1,DISP-NEW,RECORDS-100,EXTEND-100    A new file PFILE1 is created
 ** 100 records are assigned to PFILE1 - if full, the system tries to extend it by another 100
 ** each time it fills.
 // RUN
 ** It's not necessary or valid to put an END statement after most user programs
 // SWITCH 1XXXXXXX                                    Causes U1 to be SETON in the RPG program
 // LOCAL OFFSET-1,DATA-'PROC1'      Places PROC1 in the Local Data Area
 // LOCAL OFFSET-101,DATA-'?USER?'   Substitutes the operator's User ID                        
 ** LDA becomes the external data structure (UDS) in an RPG program
 // LOAD PR102
 // FILE NAME-PAYMAST,DISP-SHR                         DISP-SHR means the file is shared
 ** Other programs can use PAYMAST at the same time
 ** NAME/LABEL is used when the RPG disk file and the actual disk file names are different.
 // RUN
 // RETURN                                             Return means go to end-of-job

In this short procedure, a number of OCL statements and procedure control expressions (PCE) are used. Comments are represented by an asterisk in column 1, or can be placed after the end of a statement.

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