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174 lines
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<meta name="DC.subject" content="control language (CL), program, description, CL procedure, introduction, control language (CL), purpose, CL procedure, advantages for using, restriction" />
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<title>CL programming</title>
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</head>
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<body id="clpro"><a name="clpro"><!-- --></a>
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<!-- Java sync-link --><script language="Javascript" src="../rzahg/synch.js" type="text/javascript"></script>
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<h1 class="topictitle1">CL programming</h1>
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<div><p>This provides tasks and concepts specific to CL programming.</p>
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<p>A <em>CL procedure</em> is a group of CL commands that tells the system where
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to get input, how to process it, and where to place the results. The procedure
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is assigned a name by which it can then be called by other procedures or bound
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into a program and called. As with other kinds of procedures, you must enter
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CL procedure source statements, compile, and bind them before you can run
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the procedure.</p>
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<p>When you enter CL commands individually (from the Command Entry display,
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for instance, or as individual commands in an input stream), each command
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is separately processed. When you enter CL commands as source statements
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for a CL procedure, the source remains for later modification if you choose,
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and the commands are compiled into a module. This module remains as a permanent
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system object that can be bound into other programs and run. Thus, CL is actually
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a high-level programming language for system functions. CL procedures ensure
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consistent processing of groups of commands. You can perform functions with
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a CL procedure that you cannot perform by entering commands individually,
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and the CL program or procedure provides better performance at run time than
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the processing of several separate commands.</p>
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<p>CL procedures can be used in batch or interactive processing. Certain
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commands or functions are restricted to either batch or interactive jobs. CL
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source statements consist of CL commands. You cannot use all CL commands as
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CL source statements, and you can use some of them only in CL procedures or
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OPM programs. CL source statements can be entered in a database source member
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either interactively from a workstation or in a batch job input stream from
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a device. To create a program using CL source statements, you must enter the
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source statements into a database source member. You can then create an ILE
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program by compiling the source member into a module and binding the module
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into a program object.</p>
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<p>CL procedures can be written for many purposes, including: </p>
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<ul><li>To control the sequence of processing and calling of other programs or
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procedures.</li>
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<li>To display a menu and run commands based on options selected from that
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menu. This makes the workstation user's job easier and reduces errors.</li>
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<li>To read a database file.</li>
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<li>To handle error conditions issued from commands, programs or procedures,
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by monitoring for specific messages.</li>
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<li>To control the operation of an application by establishing variables used
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in the application, such as date, time, and external indicators.</li>
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<li>To provide predefined functions for the system operator, such as starting
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a subsystem or saving files. This reduces the number of commands the operator
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uses regularly, and it ensures that system operations are performed consistently.</li>
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</ul>
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<p>There are many advantages in using CL procedures for an application. For
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example: </p>
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<ul><li>Because the commands are stored in a form that can be processed when the
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program is created, using programs is faster than entering and running the
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commands individually.</li>
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<li>CL procedures are flexible. Parameters can be passed to CL procedures
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to adapt the operations performed by the procedure to the requirements of
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a particular use.</li>
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<li>CL procedures can be tested and debugged like other high-level language
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programs and procedures.</li>
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<li>CL procedures and programs can incorporate conditional logic and special
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functions not available when commands are entered individually.</li>
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<li>CL procedures can be bound with procedures of other languages.</li>
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</ul>
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<p>You cannot use CL procedures to: </p>
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<ul><li>Add or update records in database files.</li>
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<li>Use printer or ICF files.</li>
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<li>Use subfiles within display files.</li>
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<li>Use program-described display files.</li>
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</ul>
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</div>
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<div>
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<ul class="ullinks">
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<li class="ulchildlink"><strong><a href="creat.htm">Create a CL procedure</a></strong><br />
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All programs are created in steps.</li>
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<li class="ulchildlink"><strong><a href="comds.htm">Commands used in CL procedures</a></strong><br />
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A CL procedure can contain only CL commands.</li>
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<li class="ulchildlink"><strong><a href="workp.htm">Use CL procedures</a></strong><br />
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This gives an overview of the types of operations performed using CL procedures</li>
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<li class="ulchildlink"><strong><a href="workv.htm">Use variables</a></strong><br />
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CL procedures consist of CL commands, and the commands themselves consist of the command statement, parameters, and parameter values.</li>
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<li class="ulchildlink"><strong><a href="contp.htm">Control processing within a CL procedure</a></strong><br />
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You can use commands to change the flow of logic within your CL procedure.</li>
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<li class="ulchildlink"><strong><a href="valvz.htm">Retrieve values that can be used as variables</a></strong><br />
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This addresses how to retrieve values such as system values and job attributes to use as variables in a procedure. Note that not every possible retrieve value is included.</li>
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<li class="ulchildlink"><strong><a href="crpro.htm">Compile CL procedures</a></strong><br />
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A CL source procedure must be compiled into a module and bound into a program before it can be run.</li>
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<li class="ulchildlink"><strong><a href="clcompiling.htm">Compile source programs for a previous release</a></strong><br />
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The <span class="cmdname">Create Control Language Program (CRTCLPGM)</span> command
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allows you to compile CL source programs to use on a previous release by using
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the target release (TGTRLS) parameter. </li>
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<li class="ulchildlink"><strong><a href="cflow.htm">Control flow and communicate between programs and procedures</a></strong><br />
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You can use the <span class="cmdname">Call Program (CALL)</span>, <span class="cmdname">Call
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Bound Procedure (CALLPRC)</span>, and <span class="cmdname">Return (RETURN)</span> commands
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to pass control back and forth between programs and procedures. </li>
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<li class="ulchildlink"><strong><a href="clpgcomm.htm">Communicate between programs and procedures</a></strong><br />
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This gives information about how programs and procedures can communicate using data queues and data areas.</li>
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<li class="ulchildlink"><strong><a href="cmdinfodoc.htm">Define and document commands</a></strong><br />
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This describes how you can define your own commands and provide documentation for them.</li>
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<li class="ulchildlink"><strong><a href="clpgcmdAPIs.htm">Use command-related APIs</a></strong><br />
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This describes application programming interfaces (APIs) and programs that can be used when working with commands.</li>
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<li class="ulchildlink"><strong><a href="allow.htm">Prompt for user input at runtime</a></strong><br />
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You can prompt the workstation user for input to a CL procedure or program.</li>
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<li class="ulchildlink"><strong><a href="pmenu.htm">Enter program source</a></strong><br />
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You can enter program source using the programmer menu.</li>
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<li class="ulchildlink"><strong><a href="cmdanalyz.htm">Use command analyzer exit points</a></strong><br />
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The exit program registration facility provides two exit points for the system.</li>
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<li class="ulchildlink"><strong><a href="apgmdbcs.htm">Application programming for DBCS data</a></strong><br />
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Special considerations must be made when designing application programs to process double-byte data or converting alphanumeric application programs to double-byte programs.</li>
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<li class="ulchildlink"><strong><a href="loadrunap.htm">Load and run an application from tape or optical media</a></strong><br />
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The <span class="cmdname">Load and Run Media Program (LODRUN)</span> command
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allows the user to load and run an application written by another user or
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a software vendor from tapes or optical media supplied by the other user.</li>
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<li class="ulchildlink"><strong><a href="tfrct.htm">Transfer control to improve performance</a></strong><br />
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The <span class="cmdname">Transfer Control (TFRCTL)</span> command calls
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the program specified on the command, passes control to it, and removes the
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transferring program from the call stack. </li>
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<li class="ulchildlink"><strong><a href="sampl.htm">Examples: CL programs and procedures</a></strong><br />
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These sample programs demonstrate the flexibility, simplicity, and versatility of CL programs.</li>
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</ul>
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<div class="familylinks">
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<div class="parentlink"><strong>Parent topic:</strong> <a href="rbam6clmain.htm">Control language</a></div>
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</div>
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<div class="reltasks"><strong>Related tasks</strong><br />
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<div><a href="defmlclhll.htm" title="This describes the format in which elements in a mixed list are passed when a command is run using CL or a high-level language.">Use CL or HLL for mixed lists</a></div>
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</div>
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</div>
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</body>
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</html>
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