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Mainline Program |
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Expanded macro code using a predefined label. |
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Expanded macro code using a generated label. |
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Expanded macro code using no labels. |
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Expanded macro code with alignment considerations. |
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Program Structure with Links to Individual Functions
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JCL for Sample Program
The following is the mainframe JCL (SIMLABJ1.jcl) required to run the mainline program. This will run on an IBM Mainframe System with MVS or on a Windows System using Micro Focus Mainframe Express.
//SIMLABJ1 JOB SIMOTIME,ACCOUNT,CLASS=1,MSGCLASS=0,NOTIFY=LRSP1
//* *******************************************************************
//* This JCL Member is provided by SimoTime Technologies *
//* (C) Copyright 1987-2019 All Rights Reserved *
//* Web Site URL: http://www.simotime.com *
//* e-mail: helpdesk@simotime.com *
//* *******************************************************************
//*
//* Text - 370 Assembler, Sample use of labels
//* Author - SimoTime Technologies
//* Date - January 01, 1997
//*
//* This 370 Assembler program provides different techniques for
//* generating unique labels or avoiding the use of labels within
//* expanded macro code.
//*
//* This set of programs will run on a mainframe under MVS or on a
//* Personal Computer with Windows and Micro Focus Mainframe Express.
//*
//* *******************************************************************
//* Step 1 of 1 This is a single step job.
//*
//SIMLABS1 EXEC PGM=SIMLABA1
//STEPLIB DD DSN=SIMOTIME.DEMO.LOADLIB1,DISP=SHR
//*
Source Code for Mainline Program
The following is the mainframe assembler source code (SIMLABA1.mlc) for the mainline program that incorporates the use of the macro files to demonstrate the various ways to create label names or avoid creating label names within a macro.
SIMLABA1 CSECT
***********************************************************************
* SIMLABA1.MLC - This is an HLASM Program *
* Provided by SimoTime Technologies *
* (C) Copyright 1987-2019 All Rights Reserved *
* Web Site URL: http://www.simotime.com *
* e-mail: helpdesk@simotime.com *
***********************************************************************
* *
* This program illustrates techniques used in macro coding to *
* avoid creating labels or attempt to generate unique labels for *
* macro generated code. *
* *
* This program will run on an IBM Mainframe using MVS or a PC using *
* Micro Focus Mainframe Express, version 2.5 or later (MFE) with *
* the Assembler Option. *
* *
* Created: 1992/06/01, Simmons *
* Changed: 1992/06/01, Simmons, no changes to date... *
* *
***********************************************************************
*
BALR 12,0
USING *,12
***********************************************************************
* Macro generated code that uses specific labels. *
* *
* The advantage to this approach is that it is simple and easy *
* to understand. *
* *
* The disadvantage of this approach is that it may only be used *
* once in a program. A second use of this macro in the same program *
* will cause a duplicate label error. *
***********************************************************************
SIMLABM1
*
***********************************************************************
* Macro generated code that creates and uses generated labels. *
* *
* The advantage to this approach is the macro may be used more *
* than once in the same program. *
* *
* The disadvantage to this approach is that it attempts to create *
* unique labels but there is a possibility that a label may be *
* generated that is the same as another label used in the program. *
* *
* Another disadvantage is that it uses &SYSNDX that provides a *
* four digit number that is incremented. If the macro is used more *
* that once in a program and the second use of the macro is placed *
* before the original use of the macro then the name will be *
* changed because the number portion will be incremented. *
* *
* Also, the labels that are generated will appear in the symbol *
* table and may be confusing for the individual that uses the macro. *
***********************************************************************
SIMLABM2
*
***********************************************************************
* Macro generated code that avoids using labels. *
* *
* The advantage of this approach is that it does not use any labels. *
* *
* The disadvantage to this approach is that it may be confusing since *
* the branch target is define as a numeric offset. *
* *
* Also, care must be used when inserting additional code between the *
* branch instruction and the branch target. *
***********************************************************************
SIMLABM3
*
***********************************************************************
* Macro generated code with alignment considerations. *
* *
* It is never that easy. Let's take a look at a realistic example. *
* This program will pass a quoted text string to the macro. It is *
* the macro's responsibility to maintain halfword alignment. *
* *
* This is easy to do as long as the quoted text string is an even *
* number of characters. However, if the quoted text string is an odd *
* number of characters the macro must do a little extra work. *
* *
* The following illustrates the techniques used to maintain the *
* halfword alignment. The SR 15,15 instruction will be on a halfword *
* boundary for both an even and odd length message. *
***********************************************************************
SIMLABM4 'SIMLABM4, ALIGNMENT CONSIDERATIONS, EVEN'
*
SIMLABM4 'SIMLABM4, ALIGNMENT CONSIDERATIONS, ODD'
*
***********************************************************************
SR 15,15 * Set Return Code to Zero.
BR 14 * Return to Caller
*
END
Macro with Branch & Labels
The following examples will show how to use Macro Files that will generate code with Branch Instructions and unique labels.
Branch with a Specified Label
Using explicit names in the mainline code creates code that is simple and easy to understand. Using explicit labels in expanded macro code has the same advantage being that it is simple and easy to understand. The disadvantage of this approach is that the macro can only be used once in a program. A second use of this macro in the same program will cause a duplicate label error. The following macro (SIMLABM1.mac) uses explicit, hard-coded label names.
MACRO
SIMLABM1
.**********************************************************************
.* SIMLABM1.MAC - This is an HLASM Macro *
.* Provided by SimoTime Technologies *
.* (C) Copyright 1987-2019 All Rights Reserved *
.* Web Site URL: http://www.simotime.com *
.* e-mail: helpdesk@simotime.com *
.**********************************************************************
.*
.* The following BAL instruction will branch around the Define Constant
.* (DC) that follows the instruction.
.*
.* The branch target label is explicitly defined.
.*
.* This macro may only be used once in a program. A second use
.* would cause a duplicate label error message.
.*
BAL 1,HARDROCK * Branch Target is specific label.
DC AL2(4+32,0)
DC CL32'SIMLABM1, USE A SPECIFIED LABEL.'
DS 0H * Maintain halfword alignment
HARDROCK SVC 35
.*
MEND
Branch with a Generated Label
The advantage to this approach is the macro may be used more than once in the same program. The disadvantage to this approach is that it attempts to create unique labels but there is a possibility that a label may be generated that is the same as another label used in the program.
Another disadvantage is that it uses &SYSNDX that provides a four digit number that is incremented. If the macro is used more that once in a program and the second use of the macro is placed before the original use of the macro then the name will be changed because the number portion will be incremented.
Also, the labels that are generated will appear in the symbol table and may be confusing for the individual that uses the macro. The following macro (SIMLABM2.mac) uses generated label names.
MACRO
SIMLABM2
.**********************************************************************
.* SIMLABM2.MAC - This is an HLASM Macro *
.* Provided by SimoTime Technologies *
.* (C) Copyright 1987-2019 All Rights Reserved *
.* Web Site URL: http://www.simotime.com *
.* e-mail: helpdesk@simotime.com *
.**********************************************************************
.*
.* The following BAL instruction will branch around the Define Constant
.* (DC) that follows the instruction.
.*
.* The branch target label is generated by concatenating the literal
.* value of "ZLRS" with the numeric value supplied by $SYSNDX.
.*
.* This is an attempt to create and use a unique label within the
.* generated code. Once again, this is an attempt and in larger
.* programs the possiblity of generating a duplicate label increases.
.*
BAL 1,ZLRS&SYSNDX * Branch Target ZLRS plus &SYSNDX
DC AL2(4+32,0)
DC CL32'SIMLABM2, USE A GENERATED LABEL.'
DS 0H * Maintain halfword alignment
ZLRS&SYSNDX SVC 35
.*
MEND
Branch without a Label
The advantage of this approach is that it does not use any labels. The disadvantage to this approach is that it may be confusing since the branch target is define as a numeric offset. Also, care must be used when inserting additional code between the branch instruction and the branch target. The following macro (SIMLABM3.mac) avoids the use of label names.
MACRO
SIMLABM3
.**********************************************************************
.* SIMLABM3.MAC - This is an HLASM Macro *
.* Provided by SimoTime Technologies *
.* (C) Copyright 1987-2019 All Rights Reserved *
.* Web Site URL: http://www.simotime.com *
.* e-mail: helpdesk@simotime.com *
.**********************************************************************
.*
.* The following BAL instruction will branch around the Define Constant
.* (DC) that follows the instruction.
.*
.* The *+4 item takes the current address of the BAL instruction
.* location and increments the branch target address by four.
.*
.* The second +4 increments past the control information.
.*
.* The +44 then increments the branch target address by forty-four,
.* the length of the message text..
.*
.* Note: some instructions require halfword alignment so the length
.* of the DC should always be an even number.
.*
BAL 1,*+4+4+44 * Branch around literal.
DC AL2(4+44,0)
DC CL44'SIMLABM3, NO LABELS SPECIFIED OR GENERATED. '
SVC 35
.*
MEND
Provides for Alignment Considerations
It is never that easy. Let's take a look at a realistic example. The program (SIMLABA1) will pass a quoted text string to the macro. It is the macro's responsibility to maintain halfword alignment.
This is easy to do as long as the quoted text string is an even number of characters. However, if the quoted text string is an odd number of characters the macro must do a little extra work. The following macro (SIMLABM4.mac) avoids using label names and will maintain halfword alignment.
MACRO
SIMLABM4 &MSG
.**********************************************************************
.* SIMLABM4.MAC - This is an HLASM Macro *
.* Provided by SimoTime Technologies *
.* (C) Copyright 1987-2019 All Rights Reserved *
.* Web Site URL: http://www.simotime.com *
.* e-mail: helpdesk@simotime.com *
.**********************************************************************
.*
.* This macro will accept a quoted text string as a parameter.
.* This macro will calculate the length of the quoted text string
.* and maintain halfword alignment for the SVC 35 instruction. If
.* the quoted text string is an odd number of bytes then a pad
.* character is added to maintain the alignment.
.*
&MSGLEN SETA K'&MSG-2
&ALIGN SETA (K'&MSG-2)/2*2
AIF (&ALIGN NE &MSGLEN).ALIGNME
.*
.* The following BAL instruction will branch around the control
.* information and message text.
.*
BAL 1,*+4+4+&MSGLEN * Branch around literal.
DC AL2(&MSGLEN+4)
DC AL2(0)
DC C&MSG
SVC 35 * Maintain halfword alignment
AGO .END
.*
.ALIGNME ANOP
BAL 1,*+4+4+&MSGLEN+1 * Branch around literal and pad.
DC AL2(&MSGLEN+4)
DC AL2(0)
DC C&MSG
DC CL1' ' * Pad for alignment
SVC 35 * Maintain halfword alignment
.*
.END ANOP
MEND
Summary
The task of maintaining unique labels presented a bigger problem when using macros that generated code that included branch instructions. There are various techniques used to solve this problem and each has its own advantages and disadvantages. This document mat be used to assist as a tutorial for new programmers or as a quick reference for experienced programmers.
In the world of programming there are many ways to solve a problem. This documentation and software were developed and tested on systems that are configured for a SIMOTIME environment based on the hardware, operating systems, user requirements and security requirements. Therefore, adjustments may be needed to execute the jobs and programs when transferred to a system of a different architecture or configuration.
SIMOTIME Services has experience in moving or sharing data or application processing across a variety of systems. For additional information about SIMOTIME Services or Technologies please contact us using the information in the Contact or Feedback section of this document.
Software Agreement and Disclaimer
Permission to use, copy, modify and distribute this software, documentation or training material for any purpose requires a fee to be paid to SimoTime Technologies. Once the fee is received by SimoTime the latest version of the software, documentation or training material will be delivered and a license will be granted for use within an enterprise, provided the SimoTime copyright notice appear on all copies of the software. The SimoTime name or Logo may not be used in any advertising or publicity pertaining to the use of the software without the written permission of SimoTime Technologies.
SimoTime Technologies makes no warranty or representations about the suitability of the software, documentation or learning material for any purpose. It is provided "AS IS" without any expressed or implied warranty, including the implied warranties of merchantability, fitness for a particular purpose and non-infringement. SimoTime Technologies shall not be liable for any direct, indirect, special or consequential damages resulting from the loss of use, data or projects, whether in an action of contract or tort, arising out of or in connection with the use or performance of this software, documentation or training material.
Downloads and Links
This section includes links to documents with additional information that are beyond the scope and purpose of this document. The first group of documents may be available from a local system or via an internet connection, the second group of documents will require an internet connection.
Note: A SimoTime License is required for the items to be made available on a local system or server.
Current Server or Internet Access
The following links may be to the current server or to the Internet.
Explore the Assembler Connection for more examples of mainframe Assembler programming techniques and sample code.
Explore an Extended List of Software Technologies that are available for review and evaluation. The software technologies (or Z-Packs) provide individual programming examples, documentation and test data files in a single package. The Z-Packs are usually in zip format to reduce the amount of time to download.
Explore The ASCII and EBCDIC Translation Tables. These tables are provided for individuals that need to better understand the bit structures and differences of the encoding formats.
Explore The File Status Return Codes that are used to interpret the results of accessing VSAM data sets and/or QSAM files.
Internet Access Required
The following links will require an internet connect.
This suite of programs and documentation is available to download for review and evaluation purposes. Other uses will require a SimoTime Software License.
Link to an Evaluation zPAK Option that includes the program members, documentation and control files.
A good place to start is
The SimoTime Home Page
for access to white papers, program examples and product information. This link requires an Internet Connection
Explore
The Micro Focus Web Site
for more information about products (including Micro Focus COBOL) and services available from Micro Focus. This link requires an Internet Connection.
Glossary of Terms
Explore the Glossary of Terms for a list of terms and definitions used in this suite of documents and white papers.
Comments or Feedback
This document was created and is maintained by SimoTime Technologies. If you have any questions, suggestions, comments or feedback please use the following contact information.
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Company Overview
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