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Amb
New User
Joined: 12 Mar 2010
Posts: 64
Location: India
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Hi Guys,
I have the below statements to load address of var11 and var22 to ptr-1 and ptr-2 respectively.
Set address of var11 to ptr-1.
Set address of var22 to ptr-2.
Now I need to move data in var11 to var22 using the ptr-1 and ptr-2.
Can you please help me with this as I am new with pointers and also not able to find much information on internet? |
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Amb
New User
Joined: 12 Mar 2010
Posts: 64
Location: India
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sorry guys, just one change I have used the below statements
to set the values for ptr-1 and ptr-2
Set ptr-1 to address of var11.
Set ptr-2 to address of var22. |
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Bill O'Boyle
CICS Moderator
Joined: 14 Jan 2008
Posts: 2501
Location: Atlanta, Georgia, USA
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Using pointers and/or addresses, there isn't any data movement.
To point VAR22 at the data in VAR11 -
SET ADDRESS OF VAR22 TO PTR-1.
Actually, you can also issue -
SET ADDRESS OF VAR22 TO ADDRESS OF VAR11.
Which doesn't require a POINTER to be defined.
Are both VAR22 and VAR11 the same length?
If the length of VAR22 is greater than the length of VAR11, you will need reference modification to query the data.
IF VAR22 (1:LENGTH OF VAR11) =
Hopefully, your example is hypothetical, because you shouldn't mess with POINTERS/ADDRESSES unless you know what you're doing.
Bill |
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Robert Sample
Global Moderator
Joined: 06 Jun 2008
Posts: 8696
Location: Dubuque, Iowa, USA
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What does this mean?
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| Now I need to move data in var11 to var22 using the ptr-1 and ptr-2. |
COBOL does not move data using pointers -- COBOL moves data with the MOVE statement. Assuming both variables have addresses, of course. |
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Kjeld
Active User
Joined: 15 Dec 2009
Posts: 365
Location: Denmark
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In a previous topic you asked for help in determining if your module had got addresses passed for 2 variables (var11 and var22).
Don't get mislead into thinking that you should work with pointers to manipulate these variables. The previous topic gave you an answer how to test if you had valid addressability established for these 2 variables. If the test is positive (not NULL) you can use the definitions in the linkage area as usual.
If the test is negative (NULL), you should not execute any references to these variables.
This is an example:
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IF ADDRESS OF var11 = NULL
MOVE ws-default-var11 TO ws-var11
ELSE
MOVE var11 TO ws-var11
END IF.
IF ADDRESS OF var22 = NULL
MOVE ws-default-var22 TO ws-var22
ELSE
MOVE var22 TO ws-var22
END IF. |
This way the rest of your code can execute without referencing the linkage section items. You should define the ws-* variables in your module's working storage section. |
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Amb
New User
Joined: 12 Mar 2010
Posts: 64
Location: India
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Hi Guys,
Thanks for the information.
My reqirement was to move data from VAR11 to VAR22 using addresses of VAR11 and VAR22.
As suggested by Bill I am able to achieve that by setting the addresses using the below statement
| Code: |
| SET ADDRESS OF VAR22 TO ADDRESS OF VAR11. |
Just one more question:
After the above statement is executed VAR22 will contain same data as VAR11.
Let us say data type of VAR11 and VAR22 is PIC X(10).
I want VAR11(1:5) to be moved to VAR22(2:5).
How to I so this using the above SET address CODE? |
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Robert Sample
Global Moderator
Joined: 06 Jun 2008
Posts: 8696
Location: Dubuque, Iowa, USA
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| Quote: |
My reqirement was to move data from VAR11 to VAR22 using addresses of VAR11 and VAR22.
As suggested by Bill I am able to achieve that by setting the addresses using the below statement |
Statements like this prove you have no concept of what you are talking about and should not under any circumstances be attempting to use pointers or addresses in your code. You absolutely, categorically CANNOT MOVE DATA FROM VARIABLE TO VARIABLE BY CHANGING A VARIABLE'S ADDRESS! As further evidence, your question
| Quote: |
After the above statement is executed VAR22 will contain same data as VAR11.
Let us say data type of VAR11 and VAR22 is PIC X(10).
I want VAR11(1:5) to be moved to VAR22(2:5). |
is meaningless in the sense that reference modification is a MOVE and you are not talking about MOVE -- you are talking about address changes. Your question is exactly the same as asking how the READ statement calculates a total -- totally without meaning.
Let us assume your program is loaded and ready to run with your var11 and var22 defined as PIC X(10). The variables in COBOL are (note that the first columns are not actually in the computer -- anywhere):
| Code: |
Variable Memory location Data at memory location 00DD0000
var11 00DD0000 QUICKBROWNNOWISTHETI
var22 00DD000A |
So a DISPLAY of var11 would print QUICKBROWN and a DISPLAY of var22 would print NOWISTHETI. Your code executes your SET statement. What does the memory look like now?
| Code: |
var11 00DD0000 QUICKBROWNNOWISTHETI
var22 00DD0000 |
A DISPLAY of var11 would print QUICKBROWN and a DISPLAY of var22 would print QUICKBROWN. Note that the "old" data in var22 is still in memory, still in the same spot in memory -- but now you have no way to access it; in Java or C those 10 bytes would become eligible for garbage collection. Since COBOL doesn't use dynamic structures, there is no garbage collection and those bytes would retain their values until the program completes. |
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Amb
New User
Joined: 12 Mar 2010
Posts: 64
Location: India
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hi robert,
I think I should not have used the word "MOVE data"... and rather used the word "POINT data"
as suggested by you after the statement
| Code: |
| SET ADDRESS OF VAR22 TO ADDRESS OF VAR11 |
is executed
| Quote: |
| A DISPLAY of var11 would print QUICKBROWN and a DISPLAY of var22 would print QUICKBROWN |
Can you please suggest me a way wherein VAR22 would point to UICKBRO rather than QUICKBROWN?
I hope I am clear with my question now. |
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dick scherrer
Moderator Emeritus
Joined: 23 Nov 2006
Posts: 19244
Location: Inside the Matrix
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Hello,
| Quote: |
| My reqirement was to move data from VAR11 to VAR22 using addresses of VAR11 and VAR22. |
This is no requirement. . . It is also not even a good approach. . .
| Quote: |
| Can you please suggest me a way wherein VAR22 would point to UICKBRO rather than QUICKBROWN? |
As Robert has mentioned - you have no understanding of what is going on. . . A "pointer" is just that - a pointer. It points somewhere - a single somewhere - a single address. You are trying to get it to point to 2 places.
I'm not sure i actually understand what you are trying to do, but i have been "in the code" of tens of thousands of modules and no one has ever had this as a requirement.
It sounds like someone heard that pointers can be used in certain instances and the search was on to find a "requirement" that needs this. In other words - a solution in search of a problem to solve.
What are you trying to do that cannot be done with Reference Modification (which Bill suggested in the very first reply)  |
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Robert Sample
Global Moderator
Joined: 06 Jun 2008
Posts: 8696
Location: Dubuque, Iowa, USA
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| Quote: |
| Can you please suggest me a way wherein VAR22 would point to UICKBRO rather than QUICKBROWN? |
This cannot be done. VAR22 does not point to QUICKBROWN -- the byte pointed to by the address for VAR22 is Q -- because an address is a 4-byte field that points to a single byte of memory. You could use a COBOL MOVE statement to move the UICKBRO bytes to another variable, but not by using pointers or SET ADDRESS. Pointers and SET ADDRESS do not allow you to change the variable length so you get all 10 bytes (per your example) of the variable every time. |
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dbzTHEdinosauer
Global Moderator
Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne
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something to think about:
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LINKAGE-SECTION.
01 LK-VAR-11.
05 FIELD-1 PIC X(10).
05 FIELD-2 PIC X(10).
01 LK-VAR-22.
05 FIELD-1 PIC X(10).
05 FIELD-2 PIC X(10).
01 LK-VAR-33.
05 FILLER PIC X(05).
05 FIELD-1A PIC X(05).
PROCEDURE DIVISION USING LK-VAR-11.
SET ADDRESS OF LK-VAR-22 TO ADDRESS OF LK-VAR-11.
SET ADDRESS OF LK-VAR-33 TO ADDRESS OF LK-VAR-22.
MOVE FIELD-1A TO WS-VAR-1
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in the above scenario, if LK-VAR-11 contained
'12345AAAAA67890BBBBB'.
and ws-var-1 was defined as PIC X(05),
then WS-VAR-1 would contain AAAAA after the move.
once the above is understood, possibly this thread can come to an end. |
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dbzTHEdinosauer
Global Moderator
Joined: 20 Oct 2006
Posts: 6966
Location: porcelain throne
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| Code: |
WORKING-STORAGE.
01 POINTERS-AND-OTHER-STUFF.
05 SILLY-POINTER USAGE IS POINTER.
05 EVEN-MORE-BS
REDFINES
SILLY-POINTER PIC S9(08) COMP.
LINKAGE-SECTION.
01 LK-VAR-11.
05 FIELD-1 PIC X(10).
05 FIELD-2 PIC X(10).
01 LK-VAR-33.
05 FIELD-1A PIC X(05).
PROCEDURE DIVISION USING LK-VAR-11.
SET SILLY-POINTER TO ADDRESS OF LK-VAR-11
ADD 5 TO EVEN-MORE-BS
SET ADDRESS OF LK-VAR-33 TO SILLY-POINTER
MOVE FIELD-1A TO WS-VAR-1
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in the above scenario, if LK-VAR-11 contained
'12345AAAAA67890BBBBB'.
and ws-var-1 was defined as PIC X(05),
then WS-VAR-1 would contain AAAAA after the move. |
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Kjeld
Active User
Joined: 15 Dec 2009
Posts: 365
Location: Denmark
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In Cobol, the REDEFINES construct is used to address the same storage with different variable definitions.
I suggest you explore the possibilities of redefining your storage before venturing into pointer gymnastics.
| Quote: |
After the above statement is executed VAR22 will contain same data as VAR11.
Let us say data type of VAR11 and VAR22 is PIC X(10).
I want VAR11(1:5) to be moved to VAR22(2:5).
How to I so this using the above SET address CODE?
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Your additional question is not clear: Your source string (VAR11(1:5) (5 bytes) is different length than your destination string VAR22(2:5) (4 bytes)!
If your requirement is to shift the first 5 bytes of the string 1 byte, you can write:
| Code: |
MOVE VAR11(1:5) to VAR11(2:6) or
MOVE VAR11(1:5) to VAR22(2:6)
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In both cases your storage would then contain 'QQUICKROWN', assumed the starting adress of the two variables were the same. |
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