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iknow
Active User
Joined: 22 Aug 2005
Posts: 411
Location: Colarado, US
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Hi folks,
Can anyone tell me whether COBOL supports POINTERS concepts. Please give me a clear explanation on how to achieve the same. |
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priya
Moderator
Joined: 24 Jul 2003
Posts: 568
Location: Bangalore
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Yes, Cobol supports pointers as USAGE clause.
example:
01 A USAGE POINTER VALUE NULL.
01 B USAGE PONTER VALUE ADDRESS OF A. |
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khamarutheen
Active Member
Joined: 23 Aug 2005
Posts: 677
Location: NJ
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Hi frnd,
i too thought of asking this query. how is it possible in accepting and manipulating. can u give me one example plz. since in C v will b using like '&' to refer the address and '*' for the value so as like that in COBOL how can v access those pointer values in that. and Pointer array also. |
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umeshkmrsh
New User
Joined: 21 Sep 2005
Posts: 79
Location: India
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Pointer declaration
The concept of pointer was introduced along with COBOL-II. We can declare a pointer variable in COBOL II using the following working storage declaration:
05 WS-POINTER-VAR USAGE IS POINTER.
This will declare WS-POINTER-VAR as a four-byte field with can store address of any data item.
Setting addressability
A pointer variable ponts to nothing until unless we set it to point to some group or elementary element of LINKAGE SECTION. Below is an example which show you how we can point to an group element using pointer.
Example:
LINKAGE SECTION.
01 NAME-STRUCTURE.
05 FIRST-NAME PIC X(15).
05 SECOND-NAME PIC X(15).
Now in procedure division using following statement to set the addressability:
SET WS-POINTER-VAR TO ADDRESS OF NAME-STRUCTURE.
Note: A pointer variable can point to only LINKAGE SECTION elements.
Dereferencing a Pointer Variable
Suppose we have a pointer variable with us, say WS-POINTER-1, which points to an object(memory) having structure same as NAME-STRUCTURE declared above. Now in order to use the object pointed by the pointer variable we have to first dereference this pointer variable. Which can be done as shown below:
SET ADDRESS OF NAME-STRUCTURE TO WS-POINTER-1.
Once this has been done we can use NAME-STRUCTURE as normal variable and we will be actually working on the object pointed by the pointer WS-POINTER-1.
NOTE: Pointers can be passed as parameter to sub-programs which can then dereference it and can work on the actual object pointed by the pointer.
Some more stuff
NULL is a special pointer which points to nothing. We can set a pointer variable to NULL.
For example:
SET WS-POINTER-1 TO NULL.
We can also compare a ponter variable with another pointer variable or with NULL.
For example:
IF WS-POINTER-VAR NOT = NULL THEN
IF WS-POINTER-VAR = WS-POINTER-1 THEN
-----------------------
------------------------
END-IF
END-IF.
I hope this stuff would clear the concept of pointers in COBOL to some extent to you.
Please feal free to ask more or to share your knowledge with me. |
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khamarutheen
Active Member
Joined: 23 Aug 2005
Posts: 677
Location: NJ
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hi frnd,
thank u verymuch. let me try and inform u if i face any problem |
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iknow
Active User
Joined: 22 Aug 2005
Posts: 411
Location: Colarado, US
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Hi All,
Thanks for your reply. |
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priyesh.agrawal
Senior Member
Joined: 28 Mar 2005
Posts: 1448
Location: Chicago, IL
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Hames
New User
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Joined: 03 Oct 2005
Posts: 49
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Hi Friends,
Good work done by you all.
Till now I thought Pointer concept is not there in COBOL.
Umesh & priyesh Thanks a lot for your detailed explanation and for the link. |
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umeshkmrsh
New User
Joined: 21 Sep 2005
Posts: 79
Location: India
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| Thanks Hames and other members for these words of appreciation. |
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mmwife
Super Moderator
Joined: 30 May 2003
Posts: 1592
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Late again to the party  , but here's something I wrote a while back that uses the pointer concept to access system cntl blks.
| Code: |
CBL LIST,NOOFF
IDENTIFICATION DIVISION.
PROGRAM-ID. RUNINFO.
AUTHOR. JACK SLEIGHT.
ENVIRONMENT DIVISION.
****************************************************************
* DISPLAYS THE FOLLOWING RUN INFO FOR THE CALLING PROGRAM: *
* *
* * PGM/JOB/JOBSTEP/PROCSTEP NAMES *
* * ENTRY/LOAD/END POINTS AND LENGTH OF PROGRAM *
* *
* FOR COBOL II PROGRAMS ALSO DISPLAYS 4 BYTES OF HEX INDICAT- *
* ORS SHOWING THE COMPILE OPTIONS SELECTED AT COMPILE TIME. *
****************************************************************
CONFIGURATION SECTION.
SOURCE-COMPUTER. IBM-370.
OBJECT-COMPUTER. IBM-370.
DATA DIVISION.
FILE SECTION.
****************************************************************
WORKING-STORAGE SECTION.
****************************************************************
01 WS-TCB-ADDR-01.
10 WS-TCB-ADDR POINTER.
01 WS-CVT-ADDR-01.
10 WS-CVT-ADDR POINTER.
****************************************************************
01 WS-DISPLAY-FIELDS.
****************************************************************
10 WS-PN-DISPLAY PIC X(008).
10 WS-STEP-DISPLAY.
20 WS-JSTP-NAME PIC X(008) VALUE "NOT USED".
20 FILLER PIC X(001) VALUE "/".
20 WS-PSTP-NAME PIC X(008) VALUE "NOT USED".
10 WS-CTYPE-DISPLAY PIC X(002).
10 WS-CREL-DISPLAY PIC X(005).
10 WS-CTIME-DISPLAY PIC X(008).
10 WS-OPTBYTE-DISPLAY PIC X(008).
10 WS-CDATE-DISPLAY PIC X(012).
10 REDEFINES WS-CDATE-DISPLAY.
15 WS-CDATE-DISPLAY-RED.
20 WS-VSMO-DAY-DISPLAY PIC X(008).
20 WS-VSYEAR-DISPLAY PIC X(004).
10 WS-EP-DISPLAY PIC X(008).
10 WS-LP-DISPLAY PIC X(008).
10 WS-FP-DISPLAY PIC X(008).
10 WS-LEN-DISPLAY PIC X(008).
****************************************************************
01 WS-WORK-FIELDS.
****************************************************************
05 WS-ZERO PIC 9(009) VALUE 0 COMP.
05 WS-WORK-FP PIC 9(009) COMP.
05 WS-WORK-PACKED PIC 9(009) COMP-3.
05 REDEFINES WS-WORK-PACKED.
10 WS-WORK-X5.
20 WS-WORK-X1 PIC X(001).
20 WS-WORK-X3 PIC X(003).
05 REDEFINES WS-WORK-PACKED.
10 WS-WORK-BIN4 PIC 9(009) COMP.
05 WS-WORK-UNPACKED PIC 9(009).
05 REDEFINES WS-WORK-UNPACKED.
10 WS-WORK-UNPACKED-8 PIC 9(008).
1 /
****************************************************************
LINKAGE SECTION.
****************************************************************
01 LK-TCB-ADDR POINTER.
*--------------------------------------------------------------
*===> T A S K C O N T R O L B L O C K
*--------------------------------------------------------------
01 LK-TCB.
10 FILLER PIC X(012).
10 LK-TIOT-ADDR POINTER.
10 FILLER PIC X(028).
10 LK-LAST-CDE-ADDR POINTER.
*--------------------------------------------------------------
*===> T A S K I/O T A B L E
*--------------------------------------------------------------
01 LK-TIOT.
10 LK-JOB-NAME PIC X(008).
10 LK-JSTP-NAME PIC X(008).
10 LK-PSTP-NAME PIC X(008).
*--------------------------------------------------------------
*===> C O N T E N T S D I R E C T O R Y E N T R Y
*--------------------------------------------------------------
01 LK-CDE.
10 LK-PREV-CDE-ADDR POINTER.
10 FILLER PIC X(004).
10 LK-PGM-NAME PIC X(008).
10 LK-EP-ADDR PIC X(004).
10 LK-EXTENT-LST-ADDR POINTER.
*--------------------------------------------------------------
*===> E X T E N T L I S T
*--------------------------------------------------------------
01 LK-EXTENT-LST.
10 FILLER PIC X(009).
10 LK-PGM-LEN PIC X(003).
10 LK-LP-ADDR PIC X(004).
10 REDEFINES LK-LP-ADDR.
15 LK-LP-ADDR-BIN PIC 9(009) COMP.
10 REDEFINES LK-LP-ADDR.
15 LK-LP-ADDR-PTR POINTER.
****************************************************************
01 LK-COMPILER-INFO.
****************************************************************
05 LK-VSCOB-INFO.
10 FILLER PIC X(020).
10 LK-TYPE-VS PIC X(002).
88 LK-VSCOBOL VALUE "VS".
10 FILLER PIC X(001).
10 LK-VSREL-NBR PIC X(001).
10 FILLER PIC X(112).
10 LK-VSTIME PIC X(008).
10 LK-VSMO-DAY PIC X(008).
10 LK-VSYEAR PIC X(004).
05 REDEFINES LK-VSCOB-INFO.
10 LK-COBII-INFO.
20 FILLER PIC X(014).
20 LK-TYPE-II PIC X(002).
20 FILLER PIC X(001).
20 LK-IIREL-NBR PIC X(006).
20 LK-IIMON-DAY-YR PIC X(009).
20 LK-IITIME PIC X(008).
20 FILLER PIC X(004).
20 LK-IIOPT-BYTES PIC X(004).
1 /
****************************************************************
PROCEDURE DIVISION.
****************************************************************
000-MAINLINE.
*--------------------------------------------------------------
*===> ESTABLISH ADDRESSABILITY FOR TIOT
*--------------------------------------------------------------
MOVE X"0000021C" TO WS-TCB-ADDR-01
SET ADDRESS OF LK-TCB-ADDR TO WS-TCB-ADDR
SET ADDRESS OF LK-TCB TO LK-TCB-ADDR
SET ADDRESS OF LK-TIOT TO LK-TIOT-ADDR
*--------------------------------------------------------------
*===> SET UP STEP NAMES FOR DISPLAY
*--------------------------------------------------------------
IF LK-JSTP-NAME = SPACES
AND
LK-PSTP-NAME = SPACES
GO TO 000-CONTINUE
END-IF
IF LK-PSTP-NAME = SPACES
MOVE LK-JSTP-NAME TO WS-JSTP-NAME
ELSE
MOVE LK-PSTP-NAME TO WS-JSTP-NAME
MOVE LK-JSTP-NAME TO WS-PSTP-NAME
END-IF
.
000-CONTINUE.
*--------------------------------------------------------------
*===> SET UP PGM NAME FOR DISPLAY
*--------------------------------------------------------------
SET ADDRESS OF LK-CDE TO LK-LAST-CDE-ADDR
PERFORM WITH TEST BEFORE UNTIL LK-PREV-CDE-ADDR = NULLS
SET ADDRESS OF LK-CDE TO LK-PREV-CDE-ADDR
END-PERFORM
MOVE LK-PGM-NAME TO WS-PN-DISPLAY
*--------------------------------------------------------------
*===> SET UP ENTRY POINT ADDR FOR DISPLAY
*--------------------------------------------------------------
MOVE LK-EP-ADDR TO WS-WORK-X5
PERFORM 100-CONVERT-HEX-DATA
MOVE WS-WORK-UNPACKED-8 TO WS-EP-DISPLAY
*--------------------------------------------------------------
*===> SET UP LOAD POINT ADDR FOR DISPLAY
*--------------------------------------------------------------
SET ADDRESS OF LK-EXTENT-LST TO LK-EXTENT-LST-ADDR
MOVE LK-LP-ADDR TO WS-WORK-X5
PERFORM 100-CONVERT-HEX-DATA
MOVE WS-WORK-UNPACKED-8 TO WS-LP-DISPLAY
*--------------------------------------------------------------
*===> SET UP PGM LENGTH FOR DISPLAY
*--------------------------------------------------------------
MOVE X"00" TO WS-WORK-X1
MOVE LK-PGM-LEN TO WS-WORK-X3
PERFORM 100-CONVERT-HEX-DATA
MOVE WS-WORK-UNPACKED-8 TO WS-LEN-DISPLAY
*--------------------------------------------------------------
*===> SET UP PGM END POINT ADDR FOR DISPLAY
*--------------------------------------------------------------
COMPUTE
WS-WORK-FP = LK-LP-ADDR-BIN + (WS-WORK-BIN4 - 1)
MOVE WS-WORK-FP TO WS-WORK-X5
PERFORM 100-CONVERT-HEX-DATA
MOVE WS-WORK-UNPACKED-8 TO WS-FP-DISPLAY
*--------------------------------------------------------------
*===> SET UP COMPILER INFORMATION FOR DISPLAY
*--------------------------------------------------------------
SET ADDRESS OF LK-COMPILER-INFO TO LK-LP-ADDR-PTR
IF LK-TYPE-VS = "VS"
MOVE SPACES TO WS-CTYPE-DISPLAY
MOVE LK-VSREL-NBR TO WS-CREL-DISPLAY
MOVE LK-VSTIME TO WS-CTIME-DISPLAY
MOVE LK-VSMO-DAY TO WS-VSMO-DAY-DISPLAY
MOVE LK-VSYEAR TO WS-VSYEAR-DISPLAY
ELSE
* IF LK-TYPE-II = "C2"
MOVE "II" TO WS-CTYPE-DISPLAY
MOVE LK-IIREL-NBR TO WS-CREL-DISPLAY
MOVE LK-IITIME TO WS-CTIME-DISPLAY
MOVE LK-IIMON-DAY-YR TO WS-CDATE-DISPLAY
END-IF
DISPLAY " "
*--------------------------------------------------------------
*===> DISPLAY ALL INFORMATION PREVIOUSLY SET UP
*--------------------------------------------------------------
DISPLAY "*****************************"
"**************************************************"
DISPLAY " PROGRAM " WS-PN-DISPLAY
" RUN FROM JOB " LK-JOB-NAME
" IN STEP/PROCSTEP ===> " WS-STEP-DISPLAY
DISPLAY " COMPILED UNDER VSCOBOL" WS-CTYPE-DISPLAY
" REL " WS-CREL-DISPLAY
" AT " WS-CTIME-DISPLAY
" ON " WS-CDATE-DISPLAY
*--------------------------------------------------------------
*===> DISPLAY COBOL II OPTION BITS
*--------------------------------------------------------------
IF NOT LK-VSCOBOL DISPLAY " "
MOVE LK-IIOPT-BYTES TO WS-WORK-X5
PERFORM 100-CONVERT-HEX-DATA
MOVE WS-WORK-UNPACKED-8 TO WS-OPTBYTE-DISPLAY
DISPLAY " INDICATORS FOR COMPILER OPTIONS IN EFFECT ==> "
WS-OPTBYTE-DISPLAY
END-IF
DISPLAY " "
DISPLAY " " "ENTRY POINT " WS-EP-DISPLAY
DISPLAY " " " LOAD POINT " WS-LP-DISPLAY
DISPLAY " " " END POINT " WS-FP-DISPLAY
DISPLAY " " " LENGTH " WS-LEN-DISPLAY
DISPLAY "*****************************"
"**************************************************"
DISPLAY " "
****************************************************************
* USED TO FORCE A DUMP AT EOJ
*--------------------------------------------------------------
* COMPUTE WS-WORK-BIN4 = WS-WORK-BIN4 / WS-ZERO
****************************************************************
GOBACK
.
100-CONVERT-HEX-DATA.
*--------------------------------------------------------------
*===> CONVERTS HEX DATA FOR DISPLAY PURPOSES
* E.G. X"04FB" ====> X"F0F4C6C2" OR 04FB CHARACTER
*--------------------------------------------------------------
MOVE WS-WORK-PACKED TO WS-WORK-UNPACKED
INSPECT WS-WORK-UNPACKED CONVERTING
X"FAFBFCFDFEFF" TO "ABCDEF"
.
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khamarutheen
Active Member
Joined: 23 Aug 2005
Posts: 677
Location: NJ
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Hi frnd,
It's little big lengthy but worthy.. let us check out the coding and inform u if not clear. Thank u for ur coded reply. |
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guptae
Moderator
Joined: 14 Oct 2005
Posts: 1208
Location: Bangalore,India
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Hi,
Would u please tell me how we can access a variable using pointer.
LINKAGE SECTION.
01 NAME-STRUCTURE.
05 FIRST-NAME PIC X(15).
05 SECOND-NAME PIC X(15).
SET WS-POINTER-VAR TO ADDRESS OF NAME-STRUCTURE.
But how we can access NAME-STRUCTURE using WS-POINTER-VAR ? |
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