Assignment 1 - Your First Mainframe Program       

CSCI 360                            Assignment 1 - Your First Mainframe Program           
25 points

To Start

Before you begin this assignment, you must first allocate a PDSE (Partitioned Data Set Extended), a mainframe data set, that will hold your assignment files for the semester.  We will cover – and record – how to do this during the first week of classes.  You will be guided through allocating your partitioned data set extended (PDSE) from within IBM Developer for z/OS (IDz).  You will also be shown how to create a new "member" of the PDSE into which you will copy and edit the program below.  Please note that you won't create a new PDSE for each assignment, just a new member of that PDSE for each successive assignment this semester.

The Assignment

For 25 points, create and edit the new member of your Assignments PDSE.  You should have named the new member ASSIGN1.  When you're ready to begin editing that member, type or copy and paste the JCL (Job Control Language) and Assembly language program below that begins with the line

//KC03nnnA JOB ,'your name here',MSGCLASS=H

and ends with the line with only two forward slashes ( // ) into your PDSE member named ASSIGN1.  

When you've finished and made the editing change to it described in red in the "doc box" below, you will have what's known as a "job" that can be submitted for execution remotely on the Marist University mainframe.  By the way, you can delete the lines with the red text from your PDSE member if you choose to do so.  
 
It's important that you begin in column 1 for lines 1 through the line with MAIN on it and be sure that the final two lines begin in column 1.  In Assembler, columns make a difference so don't change the position of anything in this code.

Once you have the JCL and program typed or copy and pasted into the PDSE member named ASSIGN1, make changes to it as described in the doc box in red below.

//KC03nnnA JOB ,'your name here',MSGCLASS=H
//JSTEP01  EXEC PGM=ASSIST
//STEPLIB  DD DSN=KC00NIU.ASSIST.LOADLIB,DISP=SHR
//SYSPRINT DD SYSOUT=*
//SYSIN    DD *
*****************************************************************
*                                                               *
*  CSCI 360               ASSIGNMENT 1             SUMMER 2021  *
*                                                               *
*  DEVELOPER NAME: YOUR NAME GOES HERE                          *
*  DATE DUE:  06/18/2021                                        *
*                                                               *
*  Replace KC03nnn above with your KC-ID assigned to you by     *
*  your instructor.  DO NOT LEAVE OUT THE CAPITAL LETTER A AT   *
*  THE END OF YOUR KC-ID!  Also, put your name in all capital   *
*  letters in the first line where it says 'your name here'.    *
*                                                               *
*  Note that this documentation box does not go past column 65! *
*                                                               *
*****************************************************************
*        COL. 10
*        |     COL. 16
*        |     |
*        v     v
MAIN     CSECT
         USING MAIN,15     ESTABLISH ADDRESSABILITY ON REG 15
         LA    4,13        LOAD 13 INTO REG 4
         LA    8,6         LOAD 6 INTO REG 8
         AR    4,8         ADD REG 8'S CONTENTS TO REG 4'S
         XDUMP ,           DUMP CONTENTS OF ALL 16 REGS
         BCR   B'1111',14  UNCONDITIONAL RETURN TO CALLER (OS)
*
         LTORG             LITERAL ORGANIZATION
*
         END   MAIN
/*
//

It's very important that you not save any blank lines before or after what is presented above.  The columns on each line and where things appear here are also very important.  

In the Assembler language, columns 1, 10 and 16 are significant.  Labels like MAIN begin in column 1, instruction mnemonics like LA (Load Address) begin in column 10 and instruction operands like 3,12 begin in column 16.  All letters must be capital letters too!

Assembler language, or "Assembler", is a very unforgiving language that requires close attention to detail.  The lines of the job above that begin with at least one forward slash (/) are lines of JCL, or Job Control Language, and are not Assembler code.

We'll use the same JCL for all our programming assignments and in any examples for the remainder of the semester.  There will be minor changes with lines of information added to the end of the job but that will come later.  

The JCL above surrounds the Assembler program and is used on the mainframe to tell the operating system, z/OS, what we're trying to accomplish.  In this case, we're compiling an Assembly language program and, if that's successful, we want to execute, or "run", it.  We don't call it compiling, though, when using the Assembler; it's called "assembling" rather than "compiling".

In summary, the first line of the JCL tells the mainframe operating system, z/OS, that it's your job with your KC-ID.  The word JOB tells z/OS that the first line is the beginning of a new "job."  Note the required space between JOB and the comma.  Inside the single quotes (apostrophes which mainframers call "ticks" or "tick marks"), you can put up to 20 characters of your choice.  For this class, please put your first and last name or, if too long, your first initial, a period, a space and your last name.  The MSGCLASS=H tells the Marist system where to place your job's output when it finishes.  H is the "held" class and your job's output will be placed in the held output queue.

The line with EXEC PGM=ASSIST tells the Marist system that you want to execute the program object, or executable, named ASSIST.  A program object is what we call an "executable" on the mainframe.  (You will also hear executables called "load modules" but it's old terminology.)  ASSIST is a learning version of the mainframe Assembler that assembles, or "compiles," your program and actually executes it too but only if it assembles with no errors.

When you're done typing and you're ready to run your job and view the results, first save your work and then type SUB on the command line – the long rectangle at the bottom of the editing window – and press ENTER.  After you have closed out of the member and then you come back into it later, you will no longer see the command line but can instead either right mouse and click Submit near the bottom of the choices presented or simply press Ctrl+Alt+M.

After you submit the job, you will see the job number assigned by JES (the Job Entry Subsystem) displayed.  You might see the Getting Started tab just below the editing window.  If it's there, you can simply close it.  To be efficient, though, you need to see the Remote System Details tab.  If it is not there, go to the toolbar and click on Window  Show View  Remote System Details and you should start seeing it from then on.

Once the tab opens, you should see a list of your job or jobs.  Note that the output in the tab needs to be refreshed periodically.  To do so, right mouse click in that window and click Refresh.  Another way to view your jobs is to click on JES in the file structure window on the right and click My Jobs.  Select the job you want to review and double click on it.

When you are satisfied that the results are correct, you must get a copy of your output into a text document named ASSIGN1.txt (change the name to ASSIGN1.txt, if necessary) to submit it on Blackboard.  You will be shown how to do this within the first few days of class.

Once you have the text document on your own machine, it's VERY important that you do NOT change anything in the text document you plan to submit.  If you do, it is considered cheating!

Submit a copy of your ASSIGN1.txt file on Blackboard by the time and date it is due.