Some oddities of the TCB:
- It has a 32-byte prefix (FP register savearea), so the TCB proper (+0)
starts 32 bytes into the structure.
- The control block identifier ('TCB ') is at +100.
- The first word of the TCB proper, ie. +0 is TCBRBP, but this offset is
"fixed by architecture"!
Back in the early '70s, when I first noticed the IKJTCB macro, I speculated
that TSO was the first component to "macroize" the DSECT, and hence gave it the
IKJ prefix. I never found out the truth but it is possible that, up until that
time, offsets fixed by architecture were hard-coded rather than named.
.
.
> Date: Mon, 9 Dec 2013 15:48:03 -0600
> From: [email protected]
> Subject: Curiosity: TCB mapping macro name - why IKJTCB?
> To: [email protected]
>
> Normally, I associate the prefix IKJ with TSO. Does anybody out there know
> why the TCB mapping macro is named IKJTCB instead of IHATCB. The PSA
> mapping macro is IHAPSA. The RB map name is IHARB. The ASCB map is IHASCB.
>
> Just curious.
>
> --
> This is clearly another case of too many mad scientists, and not enough
> hunchbacks.
>
> Maranatha! <><
> John McKown
>
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