Thanks for spelling it out. I needed it. :-( :-)

And maybe it helped the young'uns. :-)

Cheers, Martin

Martin Packer,
zChampion, Principal Systems Investigator,
Worldwide Cloud & Systems Performance, IBM

+44-7802-245-584

email: [email protected]

Twitter / Facebook IDs: MartinPacker
Blog: 
https://www.ibm.com/developerworks/mydeveloperworks/blogs/MartinPacker



From:   Tom Marchant <[email protected]>
To:     [email protected]
Date:   12/02/2016 13:37
Subject:        Re: AW: Re: You thought IEFBR14 was bad? Try GNU's 
/bin/true code
Sent by:        IBM Mainframe Discussion List <[email protected]>



On Fri, 12 Feb 2016 07:19:37 +0000, Martin Packer wrote:

>But Unconditional being all 4 bits set was what I wanted elucidation on.
>Perhaps I'm being thick, or perhaps it's a special case.

Condition code has two bits, giving it four possible values, 0, 1, 2, or 
3.

The mask bits in the conditional branch instructions have four bits, each 
bit 
corresponds to one of the four possible condition code settings. For 
example, 
if the first bit (bit 0) in the instruction mask is 1, it means take the 
branch if 
the condition code is zero. If the second mask bit (bit 1) is set, it 
means take 
the branch if the condition code is one. 

If all four bits are set, it means take the branch if the value of the 
condition 
code is 0, 1, 2, or 3. Since there are no other possible values, the 
branch is 
unconditional.

-- 
Tom Marchant

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