On Wed, 16 Mar 2011 19:29:35 -0700, Charles Mills wrote:
>It would be an interesting exercise to write the simplest proper, reentrant,
>RMODE=31 assembler program that output "Hello, world" to anything other than
>the console.
Apparently not so interesting, or you'd do it.
>Anyone want to venture a guess on how many lines of code?
>Fifty? Thirty? Can anyone do it in twenty?
I can easily do it in to if I use the entry and exit macros that I normally
use to establish reentrancy and return. Without them it seems to take 28.
You could shave that to 27 by dispensing with the save area forward chain.
HELLO CSECT
STM 14,12,12(13) SAVE CALLER'S REGISTERS
LR 11,15 SET OUR BASE REGISTER
USING HELLO,11
GETMAIN RU,LV=WORKLEN,LOC=24
ST 13,4(,1) BACK CHAIN
ST 1,8(,13) FORWARD CHAIN
LR 13,1 LOAD MY SAVE AREA ADDRESS
USING WORKAREA,13
MVC OPENLIST(MESSAGE-OLIST_M),OLIST_M
OPEN (SYSPRINT,OUTPUT),MF=(E,OPENLIST)
PUT SYSPRINT,MESSAGE
CLOSE MF=(E,OPENLIST)
LR 1,13 COPY MY SAVE AREA ADDRESS
L 13,4(,13) POINT TO CALLER'S SAVE AREA
FREEMAIN RU,A=(1),LV=WORKLEN
LM 14,12,12(13) RESTORE CALLER'S REGISTERS
SLR 15,15
BR 14 RETURN TO CALLER
OLIST_M OPEN (DCB_M,OUTPUT),MF=L
DCB_M DCB DSORG=PS,MACRF=PM,DDNAME=SYSPRINT,RECFM=FB,LRECL=80
MESSAGE DC CL80'STUPID "HELLO WORLD" MESSAGE'
WORKAREA DSECT ,
DS 18F SAVE AREA
OPENLIST OPEN (SYSPRINT,OUTPUT),MF=L
SYSPRINT DCB DSORG=PS,MACRF=PM,DDNAME=SYSPRINT,RECFM=FB,LRECL=80
WORKLEN EQU *-WORKAREA
END HELLO
--
Tom Marchant
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