Portal | Manuals | References | Downloads | Info | Programs | JCLs | Master the Mainframes
IBM Mainframe Computers Forums Index
 
Register
 
IBM Mainframe Computers Forums Index Mainframe: Search IBM Mainframe Forum: FAQ Memberlist Usergroups Profile Log in to check your private messages Log in
 

 

Linkage section and pointers

 
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> COBOL Programming
View previous topic :: :: View next topic  
Author Message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Mon Oct 04, 2010 6:55 pm    Post subject: Linkage section and pointers
Reply with quote

hi guys,


My requirement is as below:


I have a prog A which is calling prog B.
Linkage section of program B is as mentioned below.
In procedure division of program B I need to access the variables ws-var1 and ws-var2
and display them.


Prog A

01 ws-var1 PIC X(3) value 'XYZ'.
01 ws-var2 PIC X(3) value 'abc'.


Call 'B' using ws-var1
ws-var2.




Prog B

Linkage section.

01 ws-var3 PIC X(1).


Procedure division.

----
----.




I understand that this needs to be done using pointers, but somehow I am not able to achieve this.
Please help.
Back to top
View user's profile Send private message

Anuj Dhawan

Senior Member


Joined: 22 Apr 2006
Posts: 6258
Location: Mumbai, India

PostPosted: Mon Oct 04, 2010 7:29 pm    Post subject:
Reply with quote

I'm not able to understand your request quite well and not sure why do you mention about pointers? Here are some threads on pointers (if you insist and want to read about them), you mihgt like to look at, however:

http://ibmmainframes.com/post-155622.html
http://ibmmainframes.com/post-135797.html
Back to top
View user's profile Send private message
GuyC

Senior Member


Joined: 11 Aug 2009
Posts: 1278
Location: Belgium

PostPosted: Mon Oct 04, 2010 7:51 pm    Post subject: Reply to: Linkage section and pointers
Reply with quote

normally it is
Prog B
Code:
Linkage Section
    01 ls-var1 pic x(3).
    01 ls-var2 pic x(3).
procedure division using ls-var1, ls-var2.
    display ls-var1 ls-var2.
Back to top
View user's profile Send private message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Tue Oct 05, 2010 12:15 pm    Post subject: Reply to: Linkage section and pointers
Reply with quote

See the problem is that two variables ws-var1 and ws-var2 are passed to program B.
And in program B there is only one variable in the linkage section ws-var3 with picture clause pic X(1).

So how do I access the variables ws-var1 and ws-var2 in program B?
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Tue Oct 05, 2010 2:06 pm    Post subject:
Reply with quote

1. how are the two variables (ws-var1 and ws-var2) being passed by program A?

2. change program b
Back to top
View user's profile Send private message
Robert Sample

Global Moderator


Joined: 06 Jun 2008
Posts: 7914
Location: Bellevue, IA

PostPosted: Tue Oct 05, 2010 4:36 pm    Post subject:
Reply with quote

Why on earth do you want to violate the normal rules of COBOL by not addressing both WS-VAR1 and WS-VAR2 in program B by using the appropriate LINKAGE SECTION and PROCEDURE DIVISION USING statements? No good can come of such violations -- even if you cobble together something that worked, it would be a nightmare to maintain.

If you cannot change program B, make a new copy of it and add both variable to the LINKAGE SECTION and PROCEDURE DIVISION USING statements. Pointers were not created to allow you to violate COBOL standards.
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Tue Oct 05, 2010 5:24 pm    Post subject:
Reply with quote

why this BS about pointers?
the program at least requires new code to deal with the new variables.

again, the TS has not given us any info,
he only wants help on how to implement the solution to which he has already arrived.

The quality of questions on this board continues to deteriorate.
Back to top
View user's profile Send private message
dick scherrer

Site Director


Joined: 23 Nov 2006
Posts: 19270
Location: Inside the Matrix

PostPosted: Tue Oct 05, 2010 8:09 pm    Post subject:
Reply with quote

Hello,

Why/how do you believe a module that "passes" 2 variables should invoke a module that is coded to use only one?

What business or technical reason is there for even trying?

If there is no real reason, implement properly (both modules will have 2 variables). If there is some reason that none of us have imagined, describe what is so special with this and someone may have a suggestion. . . icon_confused.gif
Back to top
View user's profile Send private message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Wed Oct 06, 2010 9:54 am    Post subject: Reply to: Linkage section and pointers
Reply with quote

Okay... I will explain in more detail.
Also I have googled a solution for the same.

Actual requirement is any program which calls program B can pass a data area varying from PIC X(10) to PIC X(100) to program B.

Program B will always called by reference.
Program B is supposed to display the data that is passed to it.

If the data passed to the program B varies from PIC X(10) to PIC X(100), it is not possible for me to code the linkage section in program B.

So just code a variable with PIC X(1) in the linkage section of program B and obtain all the variables that are passed to this program as below.

Code:

        01 sub-pointer usage pointer.
        01 add-pointer redefines sub-pointer pic X(4) comp-5.
               
        linkage section.
        01 link-area pic x.
       
        procedure division using link-area.
                set sub-pointer to address of link-area
                display link-area
            perform n times
                add 4 to add-pointer
                set address of link-area to sub-pointer
                display link-area
            end-perform
            exit program.



Now if Progarm A calls Program B with the below value
01 ws-var1 PIC X(3) value 'XYZ'.


Then program B will display
X
Y
Z

where value of n in program B should be 3. This value can be polpulated using a small logic.
Back to top
View user's profile Send private message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Wed Oct 06, 2010 11:13 am    Post subject:
Reply with quote

hey there was an error in what I posted above

Instead of adding 4 to add-pointer
Code:

add 4 to add-pointer



We need to add 1

Code:

add 1 to add-pointer
Back to top
View user's profile Send private message
GuyC

Senior Member


Joined: 11 Aug 2009
Posts: 1278
Location: Belgium

PostPosted: Wed Oct 06, 2010 1:17 pm    Post subject:
Reply with quote

1st : this is something completely different than the original question.
original = passing 2 variables
new = passing 1 variable of varying length.

2nd: how will n be determined ?
you could just define ls-var1 X(100). in the linkage section
and if N=3 make sure you only use the first 3 pos of ls-var1.
display ls-var1(1:n)
move spaces to ls-var (1:n)

The risk with this (or with your approach adding 1 to an address) is that when
n> actual length of the ws-var in program A you can overwrite other variables or areas of program A.
move spaces to ls-var or in your solution looping 100 times while n = 3
would be a serious mistake.

I wouldn't appreciate such programs in my environment.
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Wed Oct 06, 2010 2:01 pm    Post subject:
Reply with quote

often legacy systems have to be changed and usually some manager
has decided that the change is to be implemented with the least amount of
program change.

Some super tech has figured out how to play assembler with cobol and
provides the manager with a 'slick solution' to the problem.
then this idea gets passed to someone with little or no technical abilities.
Missing of course is the code to walk thru control blocks or registers
to pick-up little items like number of parms passed, length of parm, etc...

problem is that the
real cost to program changes is the testing involved
prior to implementation to production. But as we have seen more and more,
this testing is not done.
or as probably in this case, the cost of testing is allocated to another manager.
Back to top
View user's profile Send private message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Wed Oct 06, 2010 2:25 pm    Post subject:
Reply with quote

@GuyC

Above logic can be used for two variables also
And getting the exact value of N will not be a problem.

I agree such coding practice shud not be used but I do not have an alternative solution as we are not in a position to make multiple copies of this program B.
Also I could find a similar logic as posted above by me in one of the IBM mainframe sites.
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Wed Oct 06, 2010 3:10 pm    Post subject:
Reply with quote

AMBy wrote:
Above logic can be used for two variables also
And getting the exact value of N will not be a problem.


would you be so kind as to provide the method of determining the value of N
as well as how to provide for more than one variable (multiple parms in USING List).
Back to top
View user's profile Send private message
GuyC

Senior Member


Joined: 11 Aug 2009
Posts: 1278
Location: Belgium

PostPosted: Wed Oct 06, 2010 3:55 pm    Post subject:
Reply with quote

two variables (01 levels in WS) are located in memory on two different
adresses (base register & offset). suppose BR1:Offset1 and br2:offset2
If you're lucky and they are defined right after each other in pgmA, then br1 = br2 and offset2 = offset1 + length of var1.
But there is no guarantee that it will be so and remain so after recompile or upgrade of the compiler or something.

So I'm also very interesting how :
dbzTHEdinosauer wrote:
would you be so kind as to provide the method of determining the value of N
as well as how to provide for more than one variable (multiple parms in USING List).
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Wed Oct 06, 2010 4:25 pm    Post subject:
Reply with quote

GuyC,
you have to remember that the CALLing program generates a transfer instruction
that contains (in registers and/or data areas 'pointed to by the register') the addresses of the USING List, as well as the lengths of each structure.

Bill or another assembler tech will have to provide the exact explanation

the code generated by the PROCEDURE DIVISION USING statement,
loads addresses to associated linkage items.

the info is there, it is not easy in COBOL to access this data,
because the CALL and PROCEDURE DIVISION USING 'macros' do all the interpretation.

as the CALLed program is executed, somewhere, someplace, the allowable address ranges of the CALLing program are available to the OP-System so that it can decide whether to execute the instruction or issue a S0C4.

as i said earlier,
COBOL code to
  • walk thru the control blocks
  • access the register contents
  • interpret the data

is what I wanted AMBy to provide.

it is doable, i have done it years ago with COBOL 2.
it is just such a can of worms and you only need one clown to come along
and change something,
or do something just a little different
and it all becomes a bag of wet s..t!
Back to top
View user's profile Send private message
dbzTHEdinosauer

Global Moderator


Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne

PostPosted: Wed Oct 06, 2010 4:32 pm    Post subject:
Reply with quote

and as a side note:
the data structure referenced in a CALL USING
does not have to be a level-01. it can be anything except 66 or 88.
actually don't know about 66. I never use them, but they could be acceptable.

the data structure reference in a PROCEDURE DIVISION USING
does have to be
  • level 01 or 77
  • in linkage
Back to top
View user's profile Send private message
Amb

New User


Joined: 12 Mar 2010
Posts: 64
Location: India

PostPosted: Wed Oct 06, 2010 4:58 pm    Post subject:
Reply with quote

@ GuyC and @DBZ

Sorry for the confusion I agree with you

Quote:

two variables (01 levels in WS) are located in memory on two different
adresses (base register & offset)


What we have done is:

In the calling program A, I have two variables defined at 05 LEVELS under one group item.

Code:


       Calling Program:
       ----------------       
       Identification division.
       program-id. calling.

       data division.
       working-storage section.
       01 call-area.
        05 call-area1 pic x(6) value 'ABCDE'.
        05 call-area2 pic x(10) value '123456'.
       linkage section.
       procedure division.
            Call 'calledp' using call-area.
            stop run.
      



      Called Program:
      ---------------

       Identification division.
       program-id. calledp.

    
       working-storage section.
       01 sub-pointer usage pointer.
       01 add-pointer redefines sub-pointer pic X(4) comp-5.
       01 call-size Pic 9(3) value 20.
      
       linkage section.
       01 link-area pic x.
      
       procedure division using link-area.

           set sub-pointer to address of link-area
           display "first time: " link-area
           perform 16 times
            add 1 to add-pointer
            set address of link-area to sub-pointer
            display link-area
           end-perform
           goback.




And as far as getting the value of N is concerned. We are calling a user defined C function from prog B to achieve the same.

I will post u the same within 2 days once we are done with the testing.
Back to top
View user's profile Send private message
View previous topic :: :: View next topic  
Post new topic   Reply to topic    IBMMAINFRAMES.com Support Forums -> COBOL Programming All times are GMT + 6 Hours
Page 1 of 1

 

Search our Forum:

Similar Topics
Topic Author Forum Replies Posted
No new posts Number of parameters in Linkage kregen COBOL Programming 4 Wed Jan 27, 2016 5:13 pm
No new posts Cobol and Pointers Steve1226 COBOL Programming 4 Thu Jan 30, 2014 1:44 am
No new posts COBOL Parmlist and Associated Linkage... Bill O'Boyle COBOL Programming 10 Fri Dec 20, 2013 9:43 pm
No new posts Linkage Section for Three programs Mr.Niceguy COBOL Programming 13 Sat Jun 01, 2013 7:21 pm
No new posts Sort - Header on Page Break and Secti... srinathds83 SYNCSORT 7 Mon May 13, 2013 11:31 am


Facebook
Back to Top
 
Mainframe Wiki | Forum Rules | Bookmarks | Subscriptions | FAQ | Tutorials | Contact Us