Re: Re: Where do I start?

On Thu, May 27, 2010 at 6:14 PM, Rick Fochtman <[email protected]> wrote:

>
>
> ------------------------------------<snip>--------------------------------
>
>  This is from one of those documentation programs and it talks about
> savign the length and using r1 to
> do it.
>
>          TGET   (2),(3),R           READ FROM THE TERMINAL
>           STH    R1,0(R4)            SAVE THE LENGTH FROM TGET
>           SPACE  2
>           LR     R1,R13              COPY MY SAVE AREA POINTER
>
> btw: What does the "SPACE" directive do above?
>
>
>  SPACE 2 tells the assembler to leave two blank lines, for a
> prettier listing. Also that TGET doesn't really save much;
> shorter would be:
> 	LA	1,INBUFF
> 	LA	0,L'INBUFF
> 	ICM	1,8,=x'81'	TGET ASIS
> 	TGET	1,0,R
>
>
> -------------------------------<unsnip>---------------------------------------
> Are you planning to store in location X'000001' for zero bytes? That's what
> you're saying with "  TGET  1,0,R  ". The first TGET above tells the system
> to store the answer in the location defined by register 2, for a maximum
> length as defined in register 3. This is called "REGISTER NOTATION". :-)
>

Actually it's just someone's example code to me, All I was looking at here
was that they seem to be getting the read byte count
from R1.


>
> ------------------------------<snip>----------------------------------
>
>  The current assembler documentation is on the IBM web site, but
> much of the HL stuff doesn't apply to XF. Macros are documented
> in manuals specific to use (Using Data Sets; Assembler Services;
> etc.).
>
>
>
>  DEBUG01  TPUT     STREAM,STREAMLN,FULLSCR                               00490000
>           LA       5,1(,5)         ADVANCE OUTPUT POINTER                00500000
>
>           LA       6,1(,6)         ADVANCE INPUT  POINTER                00510000
>           SH       1,=H'1'          REDUCE BYTE COUNT                     00520000
>
>
>  The TPUT has just destroyed R1 (address of STREAM), so the loop
> will never end. One way of handling is is to use, for instance:
> 	TGET ...
> 	LTR	4,1	check for input	
> 	BNP	none	nothing read
>
> and use register 4 instead of 1 in subsequent code.
>
>
I followed Gerhard's suggestion here - Transfer the value from R1 to R4 to
work with it, I was unaware what the TPUT
macro did under the covers - and actually since it's working now I don't
need to update the screen as DISPLY is loaded
and I can retire the extra call to TPUT


>    -------------------------------<snip>------------------------------
> I think the point Gerhard is trying to make is this: awareness of register
> conventions is a MANDATORY PART of Assembler programming.  It's a lot more
> complicated, in many ways, because you're working at the machine level; you
> don't have a HLL compiler making those decisions for you "under the covers".
> And in most HLL's, you don't have to be concerned about arithmetic modes,
> because the conversions are done for you "under the covers".
>
> Rick
>  
>