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using based or defined variables


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grasshopper

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Joined: 22 Jul 2021
Posts: 12
Location: germany

PostPosted: Thu Jul 22, 2021 3:21 pm
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what is the difference between based or defined variables?

How do i define sub-level varibales for this requirement?
Given the following definition:
DCL SET CHAR (100);
The following areas are to be accessed with the help of overlays.
- from position 1 there is a 4-digit personnel number in binary format

- from position 3 on, there is the name (NAME) in the length of 15 bytes, followed by the first name (VNAME) in the same length

- from position 68 there is a 5-digit amount (BETR) with 2 decimal places (--> 5 VK, 2 NK) in unpacked format

- from position 81 there are 10 numbers in unpacked format of 2 bytes length each
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Garry Carroll

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Joined: 08 May 2006
Posts: 1119
Location: Dublin, Ireland

PostPosted: Thu Jul 22, 2021 4:26 pm
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BASED variables are addressed using POINTERS or ADDRESS of, A DEFined variable is defined on an absolute POSition within another variable. I find based variables preferable since a change of an underlying variable will result in recalculation of the address/pointer while something defined an an absolute position does not change its offset.

Several ways of overlaying... though using SET as a variable name is a BAD idea...

Code:
DCL 1      OVERLAY    BASED ADDR(SET),
         3    PERSONNEL_NUM  BIN FIXED(15),
         3    FULL_NAME,
            5 SURNAME              CHAR(15).
            5 LASTNAME             CHAR(15),
          3   FILLER1                 CHAR(nn),
          3   BETR                     PIC'(999V99),
          3   FILLER2                 CHAR(nn),
          3   NUM_ARRAY(10),
            5 PIC('99');   


You can calculate the size of the fillers. Also, please use code tags where appropriate - as I have done.


Garry.
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grasshopper

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Joined: 22 Jul 2021
Posts: 12
Location: germany

PostPosted: Sun Jul 25, 2021 9:12 pm
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Garry Carroll wrote:
BASED variables are addressed using POINTERS or ADDRESS of, A DEFined variable is defined on an absolute POSition within another variable. I find based variables preferable since a change of an underlying variable will result in recalculation of the address/pointer while something defined an an absolute position does not change its offset.

Several ways of overlaying... though using SET as a variable name is a BAD idea...

Code:
DCL 1      OVERLAY    BASED ADDR(SET),
         3    PERSONNEL_NUM  BIN FIXED(15),
         3    FULL_NAME,
            5 SURNAME              CHAR(15).
            5 LASTNAME             CHAR(15),
          3   FILLER1                 CHAR(nn),
          3   BETR                     PIC'(999V99),
          3   FILLER2                 CHAR(nn),
          3   NUM_ARRAY(10),
            5 PIC('99');   


You can calculate the size of the fillers. Also, please use code tags where appropriate - as I have done.


Garry.


Thanks Garry. I am learning PL1 and trying to learn it with your solutions and then refering them back to the manual also. This helps me understand the manual better. THANK YOU.
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