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#1: Lengths of fields Author: misi01, Location: Stockholm, Sweden

Posted: Tue Apr 17, 2018 7:27 am
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I'm trying to get my head around the following problem and simply don't understand it. I'm guessing that maybe the usage of COMP-5 and SYNC might have something to do with it but would appreciate if anyone can explain.
Here's the source code for part of a copybook layout. The copybook looks like this:-

Code:

01 XWU92001-Addon.
03 Addon.
06 attr-nil-Addon-value PIC X DISPLAY.

06 MonthlyPrice-num PIC S9(9) COMP-5 SYNC.

06 MonthlyPrice PIC S9(9) COMP-5 SYNC.

06 Name-num PIC S9(9) COMP-5 SYNC.

06 Name.
09 Name2-length PIC S9999 COMP-5 SYNC.
09 Name2 PIC X(255).
09 attr-nil-Name-value PIC X DISPLAY.
06 filler PIC X(2).

Nothing more in the copybook

and the resulting compiler listing looks like this

Code:

01 XWU92001-Addon. BLW=00001+3E0 0CL276
03 Addon. BLW=00001+3E0 0CL276
06 attr-nil-Addon-value PIC X DISPLAY. BLW=00001+3E0,0000000 1C
06 MonthlyPrice-num PIC S9(9) COMP-5 SYNC. BLW=00001+3E4,0000004 1F
06 MonthlyPrice PIC S9(9) COMP-5 SYNC. BLW=00001+3E8,0000008 1F
06 Name-num PIC S9(9) COMP-5 SYNC. BLW=00001+3EC,000000C 1F
06 Name. BLW=00001+3F0,0000010 0CL258
09 Name2-length PIC S9999 COMP-5 SYNC. BLW=00001+3F0,0000010 1H
09 Name2 PIC X(255). BLW=00001+3F2,0000012 255C
09 attr-nil-Name-value PIC X DISPLAY. BLW=00001+4F1,0000111 1C
06 filler PIC X(2). BLW=00001+4F2,0000112 2C

My assumption is that the various fields have the following lengths:-

Code:

Field
length
06 attr-nil-Addon-value 1 (pic x display)
06 MonthlyPrice-num 4 PIC S9(9) COMP-5 SYNC.
06 MonthlyPrice 4 PIC S9(9) COMP-5 SYNC.
06 Name-num 4 PIC S9(9) COMP-5 SYNC.
06 Name. (group variable - ignore)
09 Name2-length 2 PIC S9999 COMP-5 SYNC.
09 Name2 255 PIC X(255).
09 attr-nil-Name-value 1 PIC X DISPLAY.
06 filler 2 PIC X(2).

Now when I add up 1+4+4+4+2+255+1+2 I get 273, and not 276 as the compiler listing shows.
What am I missing ?

#2: Author: Terry_Heinze, Location: Richfield, MN, USA

Posted: Tue Apr 17, 2018 8:32 am
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I don't know assembler, but my guess is that the compiler inserted 2 "slack bytes" before 06 Name to force Name2-length to start on a half-word boundary (because of the SYNC clause).

#3: Author: kolusu, Location: San Jose

Posted: Tue Apr 17, 2018 11:26 am
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misi01,

When using binary storage (binary and comp), COBOL compiler requires that a numeric field start on some boundary. If you specify a comp field in the middle of a record, and it doesn't happen to begin on a 32 bit (4 byte) boundary, the compiler will "align" it to a 32 bit boundary to "synchronize" it.

Check this link which explains in detail about the Slack bytes with a pictorial reprenstation

http://publibz.boulder.ibm.com/cgi-bin/bookmgr_OS390/BOOKS/igy3lr50/5.3.16.2

#4: Author: misi01, Location: Stockholm, Sweden

Posted: Wed Apr 18, 2018 2:08 am
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Thanks to both of you. As you pointed out, attr-nil-Addon-value is offset 1 and one byte. Normally, MonthlyPrice-num would then be at offset 2, but since it's a binary field, the offset is set to 4, and 4 - 1 is the same as 276 - 273.

BTW - useful link Kolusu.

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