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What are Assembler directives ?

 
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Harsh Pawar

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Joined: 04 Jun 2008
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PostPosted: Thu Jul 23, 2009 12:00 pm    Post subject: What are Assembler directives ?
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I understand that Assembler directives are instructions that direct the assembler to do something. Directives does not take any space in memory. ex: EQU , DS....

But when we write DS 1H it takes 2 bytes of memory so is it(DS 1H) a directive ?
Why we get S0C1 when we write DS 1H in our CSECT ??

Regards,
Harry.
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Robert Sample

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PostPosted: Thu Jul 23, 2009 2:57 pm    Post subject:
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DS 1H is defining two bytes of memory -- Define Storage 1 Halfword. It is not a directive because those two bytes become part of your load module. Depending on what else the program does (such as initializing them to something, perhaps), having two bytes of undefined value in the middle of your program is an excellent way to generate a S0C1 abend.
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dick scherrer

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PostPosted: Thu Jul 23, 2009 8:28 pm    Post subject:
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Hello,

Quote:
But when we write DS 1H it takes 2 bytes of memory
Why did you do this? Where is it placed in the code?
Quote:
Why we get S0C1 when we write DS 1H in our CSECT
We don't. . . If this is defined in the middle of some executable instructions, an 0c1 is quite likely.

The DS 1H can be considered a "working storage" field and it is never a good idea to try to execute working storage. . .
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