Z-System Corne� (c)
                                by Jay Sage
                       The Computer Journal, Issue 43
                         Reproduced with permission
                          of author and publisher


  Thi� �tim� �m� �colum� �i� goin� t� b� quit� �short� � I� �respons� �t� �m� �
requests� �� numbe� o� author� hav� submitte� som� ver� interestin� �articles� �
bu� �ther� ha� no� bee� enoug� spac� t� prin� them�  � wan� t� mak� sur� �tha� �
thos� �article� �ar� no� delaye� further�  On� o� the� i� o� �th� �super� �LS� �
histor� shel� b� Ro� Friefeld� wh� ha� contribute� quit� � numbe� o� excellen� �
�-Syste� �program� (SALIAS� VCOMP� an� BCOMP� t� nam� � few)�  Yo� shoul� �no� �
mis� tha� article.

  Afte� �workin� �firs� �wit� th� origina� �-Syste� �histor� �shel� �(HS� �b� �
Michae� �Rubenstein� an� the� wit� EAS� b� Pau� Pomerleau� i� occurre� �t� �m� �
tha� �i� �woul� �b� eve� nice� t� hav� � ful�-scree� histor� �shell� � Wha� �� �
envisione� �wa� bringin� th� ful� resource� o� � wordprocesso� t� bea� o� �th� �
comman� �transcript� �s� �tha� �command� coul� �b� �easil� �viewed� �modified� �
reordered� �an� �regrouped�  I� th� histor� fil� wer� � standar� �ASCI� �file� �
the� �on� �coul� �massag� �th� fil� wit� � standar� �edito� �o� �eve� �prepar� �
'history� script� i� advanc� fo� specia� purposes.

  Afte� �seein� �th� splendi� ful�-scree� wor� Ro� Friefel� ha� don� �i� �hi� �
SALIA� �(Scree� �ALIA� editor)� � aske� hi� i� h� woul� tak� o� �th� �tas� �o� �
writin� �suc� �� histor� shell�  H� did� an� h� ha� don� � �splendi� �job� � � �
would� �therefore� �lik� �t� �publicl� �tak� �credi� �fo� �tha� �al�-importan� �
managemen� skil� o� askin� th� righ� perso� t� d� � job!


                         Softwar� Updat� Service

  Whil� Echelo� wa� stil� i� busines� marketin� th� �-System� the� offere� �� �
ver� �nic� �produc� calle� SU� o� Softwar� Updat� Service� � Peopl� �wh� �hav� �
modem� an� � nearb� �-Nod� o� RCP/� syste� generall� d� no� hav� muc� �troubl� �
pickin� �u� �th� lates� release� o� publi�-domai� �-Syste� �an� �genera� �CP/� �
software� � However� fo� thos� wh� d� no� hav� modem� o� fo� who� th� �neares� �
�-Nod� �i� a� expensiv� lon�-distanc� call� obtainin� � ful� se� �o� ��-Syste� �
tool� �o� keepin� u� wit� ne� release� i� muc� mor� difficult�    Th� �Echelo� �
SU� �wa� �designe� t� solv� tha� proble� b� makin� th� materia� �availabl� �o� �
diskett� b� mail�  I� wa� � dis� subscriptio� service� an� roughl� ever� mont� �
subscriber� woul� ge� � diskett� ful� o� publi�-domai� software.

  � �a� happ� t� announc� tha� SU� i� comin� back� thank� t� th� �urgin� �an� �
energ� o� Chri� McEwen� syso� o� th� Socrate� �-Nod� (#32)� i� Plainfield� NJ�  �
Chri� an� Bil� Tishey� togethe� wit� Sag� Microsystem� East� wil� b� �offerin� �
a� �eve� mor� extensiv� servic� tha� Echelon's�  Bil� Tishey� a� mos� �o� �yo� �
know� �ha� �fo� �som� tim� bee� maintainin� � �complet� �catalo� �o� ��-Syste� �
program� �(ZFILESnn.LST� an� � compendiu� o� HL� file� coverin� al� �o� �them�  �
A� �frequen� �intervals� �Bil� release� a� updat� LB� wit� al� �th� �ne� �hel� �
files� � Now� �i� �additio� t� tha� service� Bil� �wil� �b� �puttin� �togethe� ��diskette� wit� th� softwar� a� wel� a� th� documentation.

  Thi� �mean� tha� yo� wil� b� abl� t� purchas� diskette� wit� �th� �complet� �
se� �o� �-Syste� program� and/o� subscrib� t� � monthl� updat� service� � Bil� �
an� �Chri� wil� b� handlin� mos� o� th� diskett� production� SM� �wil� �handl� �
th� order� an� bookkeepin� an� wil� produc� diskette� i� th� fe� format� �tha� �
Chri� an� Bil� canno� handl� (8� IB� SSSD� NorthSta� har�-sector� an� �Amstra� �
3").

  W� hav� no� ye� worke� ou� al� th� pricin� detail� fo� al� th� options� bu� �
b� �th� tim� yo� ar� readin� thi� column� w� wil� hav� flyer� �availabl� �wit� �
al� �th� information�  Jus� dro� m� � lette� o� postcard� o� leav� �� �messag� �
fo� m� i� an� o� th� way� indicate� i� th� sideba� t� thi� column� an� � �wil� �
ge� � flye� t� you�  T� giv� yo� som� ide� o� wha� w� ar� talkin� about� � ��-�
mont� SU� subscriptio� t� � U� addres� wil� probabl� b� $4� ($� pe� disk� �an� �
� year'� subscriptio� $7� ($� pe� diskette)�  A� yo� ca� see� w� ar� tryin� t� �
kee� th� pric� ver� low�  W� reall� wan� al� o� yo� t� b� abl� t� ge� an� �us� �
al� thes� wonderfu� programs.


                         Full� Customizin� NZCOM

  M� �technica� topi� fo� thi� tim� wil� b� abou� designin� full� �customize� �
NZCO� ��-Systems�  � hav� alway� bee� satisfie� wit� th� system� tha� �ca� �b� �
produce� s� easil� usin� th� MKZC� (MaK� nZCoM� men�-drive� utility� an� s� �� �
neve� �reall� �delve� �int� �thi� are� ver� much�  Abou� � �wee� �o� �s� �ago� �
however� �Dav� Goodma� brough� th� proble� t� me�  H� ha� � NorthSta� �Horizo� �
wit� �a� ad�-o� har� disk� an� th� operatin� syste� ha� � RO� stuc� �somewher� �
i� �th� middl� o� th� addres� space�  Tha� lef� som� disjoin� block� �o� �fre� �
memory� �an� Dav� reall� wante� t� mak� us� o� al� th� space�  � tol� �hi� �m� �
standar� answe� t� tha� problem.

  I� sectio� � (especiall� subsectio� 5.2.3� o� th� NZCO� manual� � poin� ou� �
tha� th� NZCO� syste� i� define� b� � descripto� fil� an� tha� thi� fil� (wit� �
typ� �ZCM� �i� � pur� ASCI� fil� tha� ca� b� edite� wit� one'� �favorit� �tex� �
editor�  Th� manua� recommend� tha� everyon� mak� certai� change� s� tha� �th� �
descripto� wil� properl� reflec� th� user'� hardwar� environment� suc� a� �th� �
dis� �drive� �availabl� an� th� characteristic� o� th� �system'� �printe� �an� �
terminal.

  � �di� �no� �actuall� �com� ou� an� sa� i� �explicitly� �bu� �ther� �i� �a� �
implicatio� tha� othe� value� i� th� ZC� fil� ca� als� b� changed�  Th� �trut� �
is� � believe� tha� � avoide� thi� subjec� i� par� becaus� � wa� no� �entirel� �
sur� whic� value� coul� an� whic� value� coul� no� b� changed�  M� �suggestio� �
t� Dav� Goodma� wa� tha� h� experimen� wit� designin� � custo� memor� ma� �fo� �
hi� �system� edi� th� value� int� th� ZC� file� an� se� wha� happene� whe� �h� �
trie� t� loa� it.

  Dave'� �repor� �bac� �t� �me� no� confirme� b� m� �ow� �experiment� �o� �m� �
Televide� �803H� �indicate� �tha� �AL� �value� �ca� �b� �changed� � Th� ��onl� �
requiremen� �i� �tha� �th� �value� �provid� �� �memor� �ma� �wit� �n� �module� �
overlapping� � Whe� �yo� �us� MKZC� t� desig� th� system� i� �take� �ove� �th� ��responsibilit� �fo� �generatin� �� �vali� memor� map� i� �yo� �d� �th� �desig� �
yourself� yo� bette� b� careful.

� Helpfu� Utility

  Thi� �suggest� � ver� nic� utilit� progra� tha� som� thoughtfu� sou� �coul� �
contribut� �t� �th� community�  Thi� utilit� (let'� cal� i� ZMAP� migh� �d� �� �
numbe� o� helpfu� things�  First� i� coul� display� perhap� i� som� �graphica� �
o� sem�-graphica� way� th� memor� ma� o� � �-System� th� on� actuall� �runnin� �
o� �on� specifie� i� th� for� o� � ZC� o� EN� fil� (an� mayb� eve� th� �Z3PLU� �
descripto� �fil� �o� typ� Z3P)�  Presen� utilities� suc� a� SHO� �(ZSHOW� �an� �
Z3LOC� lis� th� modul� addresse� i� � fixe� order� no� i� orde� o� �increasin� �
memor� �address�  Thu� the� ar� no� ver� helpfu� i� determinin� i� �ther� �ar� �
gap� �o� �overlap� i� th� map�  Ideally� ZMA� woul� fla� an� suc� �defect� �o� �
potentia� defect� i� th� ma� s� tha� the� coul� b� correcte� befor� the� caus� �
harm.

  Th� fina� ite� o� m� wishlis� �� an� thi� migh� bette� b� implemente� i� �� �
second� �independen� progra� (ZDESIG� perhaps� �� woul� b� � genera� ��-Syste� �
designer� alon� th� line� o� MKZC� bu� withou� it� restrictions�  On� woul� b� �
abl� t� specif� th� orde� o� al� th� module� i� memor� an� thei� sizes�  Give� �
th� �highes� memor� addres� available� th� progra� woul� the� figur� �ou� �an� �
displa� �th� memor� map�  On� shoul� b� abl� easil� t� alte� th� orde� o� �th� �
modules� an� on� shoul� b� abl� t� overrid� specifi� addresse� t� creat� �gap� �
i� �necessar� (bu� no� t� forc� overlaps)�  Onc� th� desire� syste� �ha� �bee� �
designed� �th� �progra� �shoul� writ� ou� � ZC� o� EN� fil� fo� �it� � Suc� �� �
progra� i� � goo� candidat� fo� implementatio� wit� � hig� leve� languag� suc� �
a� �BD� �� �o� �Turb� �Pascal�  An� i� sur� woul� �hav� �helpe� �m� �wit� �th� �
experiment� �tha� �� �a� �abou� t� �describ� �(severa� �mistake� �resulte� �i� �
crashes).

M� Experiments

  Fig� �� �show� � printou� o� th� standar� NZCOM.ZC� fil� �o� �m� �Televide� �
803H�  I� ha� alread� bee� customize� i� severa� way� usin� MKZCM�  First� �i� �
allocate� � �-recor� VBIOS�  � us� � versio� tha� fixe� th� 803'� fau� pa� �o� �
clobberin� th� inde� register� durin� BIO� call� an� implement� � chec� o� th� �
�-Syste� �driv� vecto� fo� BIO� dis�-selec� call� a� describe� i� �� �previou� �
column�  I� als� ha� roo� fo� � 2�-recor� RCP� whic� allow� m� t� us� � �ful�-�
feature� �RC� �wit� Carso� Wilso� an� Ro� Friefeld'� residen� �histor� �shell� �
CLE� (se� RCPZRL11.LB� o� �-Nodes).

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E606 CBIOS      0080 ENVTYP     E3F4 EXPATH     0005 EXPATHS    D300 RCP
0014 RCPS       0000 IOP        0000 IOPS       DD00 FCP        0005 FCPS
DF80 Z3NDIR     0023 Z3NDIRS    E400 Z3CL       00CB Z3CLS      E280 Z3ENV
0002 Z3ENVS     E200 SHSTK      0004 SHSTKS     0020 SHSIZE     E380 Z3MSG
E3D0 EXTFCB     E4D0 EXTSTK     0000 QUIET      E3FF Z3WHL      0004 SPEED
0010 MAXDRV     001F MAXUSR     0001 DUOK       0000 CRT        0000 PRT
0050 COLS       0018 ROWS       0016 LINS       FFFF DRVEC      0000 SPAR1
0050 PCOL       0042 PROW       003A PLIN       0001 FORM       0000 SPAR2 �0000 SPAR3  0000 SPAR4      0000 SPAR5      BB00 CCP        0010 CCPS
C300 DOS        001C DOSS       D100 BIO        0000 PUBDRV     0000 PUBUSR

Figur� �1� � Th� ZC� descripto� fil� fo� th� norma� NZCO� syste� � us� �o� �m� �
Televide� 803� computer.

����������������������������������������������������������������������������-
  � �decide� �t� b� cautious� especiall� afte� on� o� m� ne� �syste� �design� �
cause� th� syste� t� hang� an� � mad� � serie� o� systems� eac� differen� fro� �
th� �previou� on� i� � relativel� smal� way�  � a� no� goin� t� sho� �yo� �al� �
th� �step� �alon� th� wa� bu� wil� g� righ� t� th� �mos� �radicall� �differen� �
version�  Se� Fig� 2�  I� yo� loo� carefully� � thin� yo� wil� fin� tha� �onl� �
th� �comman� �lin� buffe� (Z3CL� i� stil� i� th� sam� plac� a� i� wa� �i� �th� �
origina� syste� (bu� i� i� bigge� now).

-----------------------------------------------------------------------------

E606 CBIOS      0080 ENVTYP     E3F4 EXPATH     0005 EXPATHS    D700 RCP
0014 RCPS       0000 IOP        0000 IOPS       D480 FCP        0005 FCPS
D200 Z3NDIR     0023 Z3NDIRS    E400 Z3CL       00FB Z3CLS      E180 Z3ENV
0002 Z3ENVS     E100 SHSTK      0004 SHSTKS     0020 SHSIZE     E280 Z3MSG
E2D0 EXTFCB     E300 EXTSTK     0000 QUIET      E2FF Z3WHL      0004 SPEED
0010 MAXDRV     001F MAXUSR     0001 DUOK       0000 CRT        0000 PRT
0050 COLS       0018 ROWS       0016 LINS       000F DRVEC      0000 SPAR1
0050 PCOL       0042 PROW       003A PLIN       0001 FORM       0000 SPAR2
0000 SPAR3      0000 SPAR4      0000 SPAR5      BA00 CCP        0010 CCPS
C200 DOS        001C DOSS       D000 BIO        0000 PUBDRV     0000 PUBUSR

Figur� 2�  � radicall� reconfigure� NZCO� syste� produce� b� manuall� �editin� �
th� ZC� file.

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  Perhap� yo� ar� wonderin� wh� � didn'� mak� th� mos� dramati� demonstratio� �
possibl� b� changin� absolutel� ever� addres� (an� perhap� size� too)� � Well� �
ther� �wa� �a� extr� constrain� tha� � wa� explorin� wit� thi� system� � � �a� �
runnin� �ZDDOS� an� � hav� specifie� tha� th� cloc� drive� b� loade� int� �th� �
s�-calle� �use� �buffer�  � hav� eve� applie� th� NZCO� �patc� �(NZCOMPAT.HEX� �
tha� come� wit� th� ZSDOS/ZDDO� packag� s� tha� whe� ne� syste� configuration� �
ar� �loaded� �th� cloc� drive� wil� b� reconnecte� t� �th� �DO� �automaticall� �
withou� th� nee� fo� runnin� LDTI� again.

  I� yo� kno� � lo� abou� �-System� yo� wil� kno� tha� ther� i� n� suc� thin� �
a� �� use� buffer�  Th� use� buffe� i� � specia� creatur� o� NZCOM� i� i� �no� �
define� �i� th� �-Syste� environmen� descripte� (o� �� loo� closel� �� i� �th� �
ZC� file)�  How� then� doe� on� determin� wher� thi� specia� ga� i� th� memor� �
ma� o� a� NZCO� syste� i� located�  Tha� i� exactl� wha� � wondere� myself�  � �
coul� �hav� �calle� ZDO� author� Ca� Cotril� o� Ha� Bowe� an� aske� �the� �ho� �
the� �infe� it� location� bu� � decide� t� experimen� instead�  Wha� �� �foun� �
afte� �variou� trial� an� error� wa� tha� th� NZCO� patc� seeme� t� �b� �happ� �
an� �abl� �t� fin� th� LDTI� cloc� modul� s� lon� a� th� comman� �lin� �buffe� �
staye� �i� th� sam� place�  Apparently� th� assumptio� i� mad� tha� �th� �use� ��buffe� �i� th� memor� fro� 100� abov� th� star� o� th� comman� lin� buffe� �u� �
t� th� rea� CBIO� (E40� t� E5F� i� m� case).

  � �di� �no� perfor� exhaustiv� test� o� thi� hypothesis�  Le� u� �jus� �sa� �
tha� �i� i� no� terribl� pruden� t� tr� t� mak� us� o� � 'use� buffer� wit� �� �
full� �customize� system�  I� woul� b� wise� t� desig� th� syste� wit� �� �ga� �
belo� th� CBIO� fo� th� cloc� drive� an� t� creat� � versio� o� LDTI� wit� �a� �
explici� �loa� �address�  Th� NZCOMPA� patc� shoul� b� omitte� fro� �NZCO� �i� �
suc� custo� system� ar� goin� t� b� used.

A Few Bugs

  Ther� �wer� �� �fe� bug� i� NZCO� tha� surface� durin� �thi� �testin� �tha� �
sugges� tha� NZCOM.CO� wa� no� quit� designe� t� wor� rigorousl� an� t� handl� �
th� �mos� �genera� �syste� loadin� situations�  Sometime� �� �foun� �tha� �ND� �
module� �becam� empty� an� th� comman� searc� pat� wa� rarel� �preserve� �wit� �
thes� systems�  Cod�-containin� modules� suc� a� th� FCP� RCP� DOS� an� s� on� �
canno� �b� �move� �fro� on� addres� t� another� � I� �thei� �startin� �addres� �
changes� �th� �cod� mus� b� reloade� fres� fro� th� ZR� file� � O� �th� �othe� �
hand� �module� tha� contai� data� suc� a� th� NDR� shel� stack� path� �messag� �
buffer� �an� �s� on� ca� an� shoul� b� move� t� an� ne� address� �s� �lon� �a� �
ther� i� roo� fo� th� ol� content� i� th� ne� home�  NZCO� sometime� faile� t� �
d� this�  Mayb� no� tha� � hav� uncovere� thes� smal� problems� � ca� pas� th� �
informatio� �o� �t� �Jo� Wright� an� h� ca� fi� u� th� cod� �t� �handl� �thes� �
situations.

[Thi� articl� wa� originall� publishe� i� issu� 4� o� Th� Compute� Journal,
P.O� Bo� 12� Sout� Plainfield� N� 0708�-001� an� i� reproduce� wit� the
permissio� o� th� autho� an� th� publisher� Furthe� reproductio� fo� no�-
commercia� purpose� i� authorized� Thi� copyrigh� notic� mus� b� retained.
(c� Copyrigh� 1990� 199� Socrate� Pres� an� respectiv� authors]