After half a century of using ICM/CLM, I find 8 and 7 to be easier to read, but 
B'1000' and B'0111' are probably clearer to the uninitiated.

NILH? I've been trying to introduce partial register instructions; the IRS 
training doesn't cover them and there's been some pushback. In all previous 
positions, I've been able to use the full repertoire available on the oldest 
installed hardware.

-- 
Shmuel (Seymour J.) Metz
http://mason.gmu.edu/~smetz3
עַם יִשְׂרָאֵל חַי
נֵ֣צַח יִשְׂרָאֵ֔ל לֹ֥א יְשַׁקֵּ֖ר




________________________________________
From: IBM Mainframe Discussion List <[email protected]> on behalf of 
Leonard D Woren <[email protected]>
Sent: Sunday, June 22, 2025 2:33 AM
To: [email protected] <[email protected]>
Subject: Re: error in post logon exit IKJEFD3 878-18 from MSTJCL


External Message: Use Caution


I've been doing that B' thing for ICM/STCM for many years, for the
reason stated -- it gives an easy visual indicator of the affected
byte(s).

OTOH, I would replace your instruction with NILH R1,X'00FF'.  No
storage ref.

/Leonard


Rupert Reynolds wrote on 6/19/2025 1:25 PM:
> It loads 1 byte from =x'00' into the high byte of R1, leaving the rest
> unchanged.
>
> Using a binary mask for ICM just makes things clearer.
>
> Roops
>
> On Thu, 19 Jun 2025, 20:40 Steve Beaver, <
> [email protected]> wrote:
>
>> Second - What are you doing with this instruction?
>>
>> ICM   R1,B'1000',=X'00'
>>
>> It makes no sense
>>
>> Steve
>>
>>
>>
>>
>>
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