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LA instruction in Assembler

 
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Swetalina

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Joined: 11 Nov 2008
Posts: 30
Location: Bangalore

PostPosted: Sun Mar 18, 2012 8:55 pm    Post subject: LA instruction in Assembler
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Hi,
I have just started assembler coding. Just wanted to know about LA instruction. When LA instruction specifies to a level, what does it mean.
For ex. LA R3,LBL1 - it will load the address of LBL1 to R3
B DSSM
...
...
LBL1 MVC instcr
XC instruc
LBL2 SH instrc

What I wanted to know is how the flow will go? R3 will have the address of LBL1 means the LBL1 and LBL2 level will be executed? Then it will branch to DSSM?

Please help me!!

Thanks!
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Bill Woodger

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Joined: 09 Mar 2011
Posts: 7306

PostPosted: Sun Mar 18, 2012 9:43 pm    Post subject: Reply to: LA instruction in Assembler
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Start to make yourself familiar with the Principles of Operation - The POP.

LA knows nothing about what is at the address which you are loading. All it is going to do is to take an address and put it in a register. What happens next is up to your code.

What do you mean by "level"?
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Robert Sample

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Joined: 06 Jun 2008
Posts: 7996
Location: Bellevue, IA

PostPosted: Sun Mar 18, 2012 9:45 pm    Post subject:
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Your post is pretty much incomprehensible since you seem to be mixing up multiple things at the same time, and you are not using the CODE button to make your code clear. Furthermore, you didn't include all of the code -- when you posted
Code:
         B     DSSM
for example -- where is DSSM label? What do you mean when you say "level" -- that term has a specific meaning on mainframes, but that meaning doesn't appear to be related to however you are using the term.

Do you understand the difference between the ADDRESS of a memory location and the CONTENTS of that memory location? If you don't understand this, you cannot understand the difference between LA and L instructions.
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