Service Manuals, User Guides, Schematic Diagrams or docs for : IBM system3 GC21-7578-2_IBM_System3_CommunicationControlProgramGeneralInformationManual_Dec75

<< Back | Home

Most service manuals and schematics are PDF files, so You will need Adobre Acrobat Reader to view : Acrobat Download Some of the files are DjVu format. Readers and resources available here : DjVu Resources
For the compressed files, most common are zip and rar. Please, extract files with Your favorite compression software ( WinZip, WinRAR ... ) before viewing. If a document has multiple parts, You should download all, before extracting.
Good luck. Repair on Your own risk. Make sure You know what You are doing.




Image preview - the first page of the document
GC21-7578-2_IBM_System3_CommunicationControlProgramGeneralInformationManual_Dec75


>> Download GC21-7578-2_IBM_System3_CommunicationControlProgramGeneralInformationManual_Dec75 documenatation <<

Text preview - extract from the document
  a
  a
  aaa
    aaaaa




                              IBMSystem,/3
                              CommunicationsControlProgram
                              GeneralInformation
                                               Manual

                              ProgramNumbers:
   aaaa
  aaaaa
 aaaaaa
            aaaaa
           aaaaaaa
          aaaaaaaaa
                                 57O2-SC1 Model10 Disk System
aaaaaaa aaaaoaaaaaa
aaaaaaa aaaaaaaaaaa
aaaa     aaaa    aaaa
                                 57O5-SC1Modet12
aaaa     aaaa    aaaa
aaaa     aaaa    aaaa
aaaoaaaaaaoa aaaaaa
aaaaaaaaaaaa aaaaaa
                                 57O4SC1 Model 15
 aaaaaaaaaa    aaaaa
  aaaaaaaa
   aaaaaa
               aaaa           Feature6033
                 aaaa
                 aaaa
                aaaaa
              aaaaaaa
 aaaa       aaaaaaaa
 aaaa      aaaaaaa
 aaaaaaaaaaaaaa
 aaaaaaaaaaaa
 aaaaaaaaaaaa
 aaaaaaaaaaaaaa
 aaaa      aaaaaaa
 aaaa       aaaaaaaa
              aaaaaaa
                aaaaa
                 aaaa
                 aaaa
   aaaa     aaaaa
  aaaaa    aaaaaaa
 aaaaaa   aaaaaaaaa
aaaaaaa aaaaaaaaaaa
aaaaaaa aaaaaaaaaaa
aaaa    aaaa     aaaa
aaaa    aaaa     aaaa
aaaa    aaaa     aaaa
aaaaaaaaaaaa aaaaaa
aaaaaaaaaaaa aaaaaa
 aaaaaaaaaa    aaaaa
  aaaaaaaa     aaaa
   aaaaaa
               aaaaaa
               aaaaaa
               aaaaaa
               aaaaaa
 aaaa            aaaa
 oaaa            aaaa
 aaaoaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaa
 aaaaaaaaaaaaaaaaaa
 aaaa            aaaa
 aaaa            aaaa
               aaaaaa
               aaaaaa
               aaaaaa
               aaaaaa
 aaaa
 aaaa




                   aaa
                   aaa aoa
                   aaa aaa
                   aaa aaa




        aaaa         aaaaaa
      aaaaa
'/ a a a a a a       aaaaaa
                     ooaaaa
aaaaaaa              aaooaa
aaaaaaa        aaaa    aaaa
aaaa           aaaaa   aaaa
aaaa           aaaaaa aaaa    tic21-7578-2
aaaa           aaaaaaaaaaa
aaaaaaaaaaaaaaaaaaa
oaaaaaaaaaa          aaaaaa   F i l eN o . 5 3 - 3 6
   aaaaaaaaaa         aaaaa
     aaaaaaaa          aaaa
        aaaaaa
T h i r d E d i t i o n ( D e c e m b e r1 9 7 5 )

T h i s i s a m a j o r r e v i s i o n o f , a n d o b s o l e t e : ; ,G C 2 1 - 7 5 7 8 ' 1 a n d T e c h n i c a l N e w s l e t t e r
G N 2 1 - 5 2 8 0 . C h a n g e sa r e i n d i c a t e d b y a v e r t i c a l l i n e a t t h e l e f t o f t h e c h a n g e ; n c w o r
e x t e n s i v e l y r e v i s e d i l l u s t r a t i o n s a r e d e n o t e d b y a b u l l e t { o ) a t t h e l e t l o f t h e f a g u r ec a p t r o n


C h a n g e s a r e p e r i o d i c a l l y m a d e t o t h e i n l o r m a t i o n h e r e i n , b e f o r e ru s i n g t h i s p u b l a c a t r o n
in connection with the operation of IBM systems,refer to Ihe IBM System/3
Eibliography,           GC20-8080, for the editions that are applicable and current.


Requests for copies of IBM publications should be made to your IBM representatavc
or to the I BM branch office servingyour locality.


Address comments concerning the contents ot this publication to IBM Corporation.
Publications, Department 245, Rochester, Minnesota 55901.                                                    Comments become
the property of lBM.




O    l n t e r n a t i o n a l B u s i n e s sM a c h i n e s C o r p o r a t i o n   1912, 1973, 1915
                                                                                                                                                       PREFACE




         T h i s m a n u i ap r o v i d e s g e n e r ad e s c r i p t i o n f t h e C o m m u n i c a t i o n C o n t r o l P r o g r a m ,
                             l            a             l                  o                                   s
         a f e a t u r eo f S y s t c m / 3M o d e l 1 0 D i s k S y s t e m ,M o d e l 1 2 , a n d M o d e l 1 5 S y s t e m
         C o n t r o lP r o g r a m m i r r g , o g r a mn u m b e r 5 7 0 2 S C 1 .5 7 0 b S C 1 ,a n d 5 7 0 4 - S C 1 ,
                                                      pr                       s          .
         r e s p e c i l v e l ' y l' t i s w r i t t e n f o r t h o s e w h o a r e r e s p o n s i b l eo r p r o v i d i n gt o t h e i r
                                      .                                                                   f
         o r g a n i z a t i o na n e f f e c t i v e o m m u n i c a t i o n s - b a s ie d o r m a t i o ns v s t e m .
                                      s                   c                                    nf

         This manual:

         o   D e s c r i b e sh e c o n c e p t , a d v a n t a g e s ,n d r e q u i r e m e n t s f a c o m m u n i c a t i o n s - b a s e d
                             t                                      a                            o
             svstem.

     .       s u r v e y st h e f a c i l i t i e so f f e r e d b y t h e c o m m u n i c a t i o n s o n t r o l p r o g r a m .
                                                                                                      c

     '       G i v e se x a m p l e so f t h e u s e o f t e r m i n a l sw i t h t h e c o m m u n i c a t i o n s o n t r o t p r o g r a m .
                                                                                                                   c

     o       I n d i c a t e s h e r e l a t i o n s h i p s e t w e e nd i s k s y s r e mm a n a g e m e n t n d t h e c o m m u n i c a -
                             t                             b                                                 a
             tions control program.

     '       L i s t st h e c o m m u n i c a t i o n st e r m i n a l sa n d f e a t u r e st h a t c a n b e u s e d w i t h t h e c o m -
             murrications ontrol proqram.
                                 c

     '       D e f i n e st h e m a c h i n ea n d p r o q r a m m i n gs y s t e m sr e q u i r e m e n t s o r i n s t a l l i n qt h i s
                                                                                                           f
             control program.

     T h i s g e n e r a li n f o r m a t i o n m a n u a l i s a n i n t r o d u c t i o n t o t h e c o m m u n i c a t i o n sc o n t r o l
     p r o g r a m a n d i t s f a c i l i t i e s ,a n d i s i n t e n d e dt o s e n r ea s a n a i d i n y o u r d e t e r m i n a t i o n
                                                                                                                                               of
     t h e u s e f u l n e s o f t h i s p r o g r a m i n s a t i s f y i n gy o u r o r g a n i z a t i o n ' sn f o r m a t i o n p r o c e s s -
                             s                                                                                  i
     ing needs.



S Y S T E M /M O D E L
             3        B

     T h e S y s t e m / 3 M o d e l 8 i s s u p p o r t e db y s y s t e m / 3 M o d e l 1 0 D i s k S v s t e m c o n t r o l
     P r o g r a m m i n g n d P r o g r a mP r o d u c t s . T h e f a c i l i t i e sd e s c r i b e di n t h i s p u b l i c a t i o nf o r
                         a
    t h e M o d e l 1 0 a r e a l s oa p p l i c a b l e o t h e M o d e l 8 , a l t h o u g h M o d e l 8 i s n o t r e f e r e n c e d .
                                                         t
    H o w e v e r ,t i ' r ei n t e g r a t e dc o m m u n i c a t i o n s d a p t e r ( l c A ) i s o n l y a v a i l a b l e n t h e
                                                                          a                                                   o
    M o d e l 8 . l f y o u h a v et h e l c A , i t i s a l w a y sd e s i g n a t e o n B S C A l i n e 2 . T h e r e f o r e ,
                                                                                              d
    y o u m u s t s p e c i f y l i n e 2 w h e n e v e ri t i s r e q u i r e d ,o r e n t e r t h e B S C A O C L s t a t e m e n t
    ( / / B S C A L I N E 2 ) a t e x e c u t i o nt i m e .


     I t s h o u l d b e rn o t e d t h a t n o t a l l d e v i c e s n d f e a t u r e sw h i c h a r e a v a i l a b l e n t h e M o d e l
                                                                    a                                                     o
    1 0 a r e a v a i l a b l e n t h e M o d e l 8 . T h e r e f o r e M o d e l 8 u s e r s h o u l db e f a m i l i a rw i t h
                               o                                             ,                     s
    the content:; of IBM System/3 Modet 8 lntroduction, GCZ| 5.114.




                                                                      ill
                                                                                                 CONTENTS




                        Control programprovided?.
Why is the Communications                                                                   "l

    W h y M i g h t I N e e dT e l e c o m m u n i c a t i o n s
    W h a t M a c h i n eC a p a b i l i t i e s r e R e q u i r e d
                                               a
    W h y W o u l d I N e e da C o m m u n i c a t i o n s o n t r o l p r o g r a m
                                                                  C




                          Control programDo?
What Doesthe Communications                                                             4

    From the Viewpoint of the Terminal Operator
    From the Viewpoint of the System Operator
    From the Viewpoint of the programmer




                         Control programbe Tailored
How Can the Communications
to My Needs?                                                                           11



How Can I Usea Communications-Based
                                 System?                                               14



                        Control programRelatedto
How is the Communications
Disk SystemManagement?                                                                 16

    T w o P r o g r a mL e v e l s
    U s eo f C o n r m u n i c a t i o n s O C S
                                         I




Terminals
        and Features
                   Supported                                                           1B



SystemConfiguration                                                                    20
                                                                             ut:::.                                I l J l \ 4 ( , l o n r n r r r r r r c ar r r g M a g r r e t r c ( l t r d
                                                                                                                                                           I
                                                                         ,d.,:::.
                                                                                                                   SELECTRIC (ETypewriter (via MLTA)




I B M 1 0 5 0 D a t a C o m m u n i c a t i o n v s t e m ( v i aM L T A )
                                              S




                                                                                           I B M 3 2 7 0 I n f o r m a t r o nD i s p l a yS y s t e m( v i a E S C A )
IBM 2740 Communication Terminal (via MLTA)




                                                                                      I B M 3 7 3 5 P r o g r a m m a b l T e r m t n a l( v i a B S C A )
                                                                                                                          e


IBM 2741 Communication Terminal (via MLTA)


                                                                                      vl
                                               e\

                                                                              't

                                                                           tt''a




                                          Remote IBM System/3 (via BSCA)




  IBM System/370 (via BSCA)




I BM 3741 Data Station




a IBM 3767 Communicatiorrs
 T e r m i n a l{ v i a M L T A )




                                    vtl
                                                                                              BSCA/MLTA Panel




                                                                                                      lni
                                                                                                      Ftrr




iBMEitem/3 Modetld DiskSystem                    wiih eiharySyncnionous
C o m m u n i c a t i oA d a p t e ( B S C A ) n d / o r u l t i p l e i n eT e r m i n a l
                       ns          r         a         M              L
Adapte(MLTA)
         r




                     vill
                                                                                                                                     SCA/MLTA Panel




o I B M s y s t e m / 3 M o d e l 1 2 w i t h B i n a r y s y n c h r o n o u sc o m m u n i c a t i o n s d a p t e r ( B S c A )
                                                                                                         A
 a n d / o r M u l t i p l e L i n e T e r m i n a lA d a p t e r ( M L T A )
                                                                                                                                            B S C A / M L T AP a n e




                                                                                                                            *i,{,*l,ij




                                                                                                                            -st!t!t{*!t,}




                                        '1
I B M S y s t e m / 3 M o d e l 5 w i t h B i n a r y S y n c h r o r r o u sC o m m u n i c a t i o n s A d a p t c r { B S C A )
a n d / o r M u l t i p l t - .L i n e T e r m i n a t A c l a p r e r ( M L T A )
W H Y I S T H E C O M M U N I C A , T I O N O N T R O LP R O G R A MP R O V I D E D T
                                          C




     T h e c o m m u n i c a t i o n s o n t r o l p r o g r a m ( C C P )p r o v i d e st h e c o n t r o l p r o g r a m s e r v i c e s
                                      c
     n e e d e d n a t e l e c o m m u n i c a t i o n s s t e mu s i n gt h e I B M S y s t e m / 3M o d e l 1 0 ,
                i                                       sy
     M o d e l 1 2 , a n d l l l o d e l 1 5 D i s k S y s t e m s .l t e n a b l e s o u t o e s t a b l i s h t e l e c o m m u n i -
                                                                                    y                         a
     c a t i o n ss v s t e mr , , r i t h i n i m u m c o s t a n d e f f o r t .
                                         m

     A brief discussionof the nered                  for, and the system requirementsfor, telecommunica-
     t i o n s m a y h e l p y o u a p p r e c i a t e h e n e e d f o r a c o m m u n i c a t i o n s c o n t r o lp r o g r a m .
                                                      t



W H Y M I G H T I N E E DT E L E C O M M U N I C A T I O N S ?

     For years,usersof large-sc;rle                  data processing            equipment have enjoyed the benefits
     o f t e l e c o m m u n i c a t i o n s .F o r o r g a n i z a t i o n s i t h t h e n e c e s s a r y q u i p m e n t ,t h e a b i l i t y
                                                                            w                             e
     to communicate ciirectly between a central computer system and a set of remotely-
     located terminals has opened new and effective approachesto satisfying their infor-
     mation processingneeds.


      T e l e c o m m u n i c a t i o n s e l p st h e d a t a p r o c e s s i n g s e r r e d u c eb o t t l e n e c k si n t h e f l o w
                                           h                                       u
      o f i n f o r m a t i o n n e e d e dt o o p e r a t ea n o r g a n i z a t i o n f f e c t i v e l y . W h e t h e r i t i s u s e d
                                                                                         e
      t o t r a n s m i t a s h i p p i n gd o c u m e n t t o t h e w a r e h o u s e h i l e a n o r d e r i s b e i n g p r o c e s s e d ,
                                                                                          w
      o r a s a m e a n so f i n q u i r i n g i n t o t h e c u r r e n t s t a t u so f a n a c c o u n t ,o r a s a w a y o f
      c a p t u r i n gd a t a a b o u t a t r a n s a c t i o nf r o m t h e v e r y s o u r c eo f t h a t t r a n s a c t i o n , e l e -
                                                                                                                                    t
      c o m m u n i c a t i o n s ; e l p sy o u g e t s i g n i f i c a n t a t a f r o m t h o s e w h o h a v e i t , a n d t o m a k e
                                    h                                      d
      c u r r e n t i n f o r m a t i o n a v a i l a L r lte D e o D l e h o n e e d i t .
                                                            o           w



W H A T M A C H I N EC A P A B I I - I T I E S R E R E O U I R E DF O R T E L E C O M M U N I C A T I O N S ?
                                             A

      In the past, the machinesnecessary establisha communications-based
                                                                   to                                                        system have
      b e e n g e n e r a l l yr - r n a v a i l a btl o u s e r so f s m a l l e rc o m p u t e r s . T h e m a c h i n e r e q u i r e m e n t s
                                                       e
      g o b e y o n d t h e c o m m u n i c a t i o n st e r m i n a l sa n d t h e m e a n so f a t t a c h i n gt h e m t o t h e
      c e n t r a l p r o c e s s i n g n i t . B e c a u s e o s t u s e r sf i n d m o r e a n d m o r e a p p l i c a t i o n si n
                                      u                       m
      w h i c h a c o m m u n i c a t i o n s - o r i e n t ea p p r o a c hc a n c u t t h r o u g h a n i n f o r m a t i o n b o t t l e -
                                                               d
      neck, telecommunicationssystems must be growing systems. The user must be f ree
      t o e x p a n d d i r e c t - a c c e ss t o r a g ec a p a c i t yt o a c c o m m o d a t ea d d i t i o n a l o n l i n e f i l e s a n d
                                              s
      to enlarge main storageto permit severalapplicationsto operate concurrently. Ex-
      pansion capability is a prerequisiteto consideration of a computer system as a com-
      m u n i c a t i o n sp r o c e s s o r .
     T h e s y s t e m / 3 o d e l10 D i s ks y s t e m , y s t e m / 3 o d e l12 , a n d t h e s v s t e m / 3 o d e l1 5
                          M                             s              M                                          M
     m e e tt h e m a c h i n ee q u i r e m e n os a c o m m u n i c a t i o n s o c e s s o r i t h t h e a v a i l a b i l i to f :
                              r                  tf                           pr            w                                    v

          Large-capacity
                       disk storage.

         H i g h l y e x p a n d a b l em a i n s t o r a q e .


         A v a r i e t y o f l i n e a n d t e r m i n a lc o n f i g u r a t i o ns u p p o r t e d y t h e m u l t i p l e l i n e
                                                                                   s                b
         t e r m i n a l a d a p t e r ( M L T A ) ; t h e b i n a r y s y n c h r o n o u s o m m u n i c a t i o n sa d a p t e r
                                                                                           c
         ( B S C A ) ;t h e l o c a l c o m m u n i c a t i o n s d a p t e r ( L C A ) o n t h e M o d e l 1 0
                                                                  a                                                  and Model 15.
         t h d i n t e g r a t e d o m m u n i c a t i o n s d a p t e r( l C A ) o n t h e M o d e l g a n d M o d e l 1 2 : a n d
                                  c                         a
         t h e d i s p l a ya d a p t e r ( D A ) o n t h e M o d e l 8 , M o d e l 1 2 , a n d M o d e l 1 5 .

     With these capabilities,the System/3 can processa broad range of communications-
     basedapplications.



W H YW O U L D N E E DA C O M M U N I C A T I O N S N T R O L R O G R A M ?
              I                                 CO          P
    A communication-basedinformation processing                                    system requiresspecialcontrol pro-
    g r a m f u n c t i o n s a s w e l l a s a s p e c i a lm a c h i n ec o n f i g u r a t i o n . T h e c o m m u n i c a t i o n s
    control program provides the necessary                          control services            for a Svstem/3 telecommuni-
    cations system.


    B e c a u s ee r m i n a l su s e c o m m u n i c a t i o n sl i n e s ,t h e p r o g r a ms u p p o r t f o r t e r m i n a l
                     t
    i n p u t / o u t p u t m u s t c o n t r o l t h o s e l i n e sa n d t r a n s l a t e h e s p e c i a ld a t a c o d e su s e d b v
                                                                                            t
    s o m e t e r m i n a l s . T h e p r o g r a m s u p p o r t t h a t g i v e sy o u r a p p l i c a t i o np r o g r a m st h e
    a b i l i t y t o r e a d f r o m a n d w r i t e t o t e r m i n a l si s a c o m p o n e n t o f S y s t e m / 3 M o d e l 1 0 ,
    M o d e l 1 2 , a n d M o d e l 1 5 D i s k S y s t e m M a n a g e m e n ti;t i s k n o w n a s t h e l o c s s u p p o r t
    for the MLTA and for the BSCA.

    B u t t h e c o m m u n i c a t i o n sI O C S p r o v i d e so n l y f o r t e r m i n a l i n p u t / o u t p u t . F u r t h e r
    program support, besidesan input/output facility, is necessary
                                                                                                        to operate a data
    processing      system effectively, even one without Jelecommunications. For example,
    control programs are required to load and execute programs from a disk library,
                                                                                                                                      to
    access    data files. and to communicate with the operator.

    A system with telecommunications requires more flexible program support tnan a
    system which performs jobs one at a time under control of one system operator.
    The effectiveness a communications-based
                       of                        system stems from its ability to per-
    form work presented,as required, by a number of operators at terminals. Operators
    are seldom aware of what other operators are doing; they may be in separaterooms,
    or in separatecities. Each request demands that a certain program be executed.
    Frequently a request arriveswhile the system is still attempting to satisfy previous
    requestsfrom other operators; the new request must be remembered and honored
    at the earliest possiblemoment. The system should be designedin such a way that
    it can execute severalprograms concurrently. In this way, the system will respond
    quickly to many operator,s requests.




                                                                    2
Program support of these capabilitieshas existed for some time on larger
                                                                                                                            computers,
m a k i n g p o s s i b l ei n f o r m a t i o n s y s t e m st h a t a r e h i g h l y e f f e c t i v ei n a v a r i e t y o f a p p l i -
cations' You may have heard such systemsdescribed in various terms, each empha-
sizing a characteristicthey possess:

                -
     Event-Driven work is performed required events
                                       as       by     which occurwithin the
     organization,
                 ratherthan in a rigid,predefined
                                                sequence.

                         -
     Transaction-oriented Eachtransactioncan be processed it happens, tne
                                                         as         so
     effectof that transaction
                             upon the organization be determined
                                                 can            immediatelv.

                     -
o Real-Time The dataheld in the system                         reflects statusof the organization,s
                                                                           the
  a c t i v i t i ea so f t h e m o m e n t , n dc a ny i e l dt r u l y c u r r e n ti n f o r m a t i o n .
                   s                        a

The first systemsof this type were used by businesses                                  with a network of many ter-
m i n a l s ,a c c e s s i n a h u g e d a t a - b a s ea n d i n v o l v i n gh u n d r e d so f a p p l i c a t i o np r o g r a m s .
                             g                          ,
Gradually, the principle of this mode of operation has also proven itself effective in
systemsof more modest scope.


N o w , t h e c o m m u n i c a t i o n s o n t r o l p r o g r a mo f f e r s t h e p r o g r a m s u p p o r t f o r a
                                           c
c o m m u n i c a t i o n s - b a s eS y s t e m / 3 M o d e l 1 0 D i s k S y s t e m ,S y s t e m / 3 M o d e l 1 2 , a n d
                                      d
S y s t e m / 3 M o d e l 1 5 . l t p r o v i d e st h o s e c o n t r o l c a p a b i l i t i e s e e d e dt o i m p r e m e n t
                                                                                                 n
a n i n f o r m a t i o n s y s t e mo f t h e t y p e d e s c r i b e d . B e c a u s e f t h e f a c i l i t i e si t o f f e r s ,
                                                                                         o
t h e e s t a b l i s h m e no f s u c h a s v s t e mc a n b e a c c o m p l s h e dw i t h a m i n i m u m c o s t
                              t                                                  i
and effort.
W H A TD O E S H EC O M M U N I C A T I O N S N T R O L R O G R A M O ?
              T                           CO          P           D




     T h e c o m m u n i c a t i o n s o n t r o l p r o g r a mp r o v i d e sc o n t r o l p r o g r a m s e r v i c e s e e d e di n
                                      c                                                                                  n
     a t e l e c o m m u n i c a t i o n s v i r o n m e n t .l t i s a n e x t e n s i o n f s y s t e m / 3 M o d e l 1 0 ,
                                       en                                                 o
     M o d e l 1 2 , a n d M o d e l 1 5 D i s k S y s t e mM a n a g e m e n t .

     T h e c o m m u n i c a t i o n sc o n t r o l p r o g r a ms u p p o r t sa n e t w o r k o f t e r m i n a l s . l t a l l o w s
     t h e t e r m i n a l st o c a l l a s y n c h r o n o u s l y p o n a s e t o f u s e r a p p l i c a t i o np r o g r a m s , h e n
                                                                  u                                                                t
     permits those programs to access common data baseconsisting of a number of
                                                            a
     d i s kf i l e s .


    T h e C C P d o e s n o t i t s e l f i n c l u d et e l e c o m m u n i c a t i o n s p p l i c a t i o np r o g r a m s( p r o g r a m s
                                                                                             a
    that access         and processyour data). They, like the application programs you may De
    w r i t i n g t o d a y , a r e n e c e s s a r i l u n i q u e t o y o u r o r g a n i z a t i o n ' s e q u i r e m e n t s .B u t t h e
                                                        y                                                 r
    ccP does control the environment in which those programs must run, and it provides
    a set of servicesupon which they can call. This relievesyou of most of the special
    requirements i n establishin g a comm un ications-based
                                                          system.


    Some of the control program servicesperformed by the communications control
    program are:

    Terminal Monitoring - The terminals of the system are monitored for program
    r e q u e s t s n d s y s t e mc o m m a n d s .
                  a

    Program Fetch - A terminal operator, or the system operator, may initiate the load-
    i n g a n d e x e c u t i o n o f a n a p p l i c a t i o np r o g r a m .


    ResourceManagement- The resources the communications-based         of                                            system (ter-
    m i n a l s ,d i s k f i l e s , m a i n s t o r a g e p a c e )a r e m a n a g e db y t h e c o m m u n i c a t i o n sc o n t r o l
                                                          s
    p r o g r a m a n d m a d e a v a i l a b l e a s r e q u i r e d ,t o e a c h a p p l i c a t i o np r o g r a m .
                                                       ,

    concurrent Program Execution - lf the system has sufficient main storage space,
    and the user so specifies,severalapplication programs for different terminals may be
    ru n concu rrentl y.

    Disk File AccessManagement - ln a system where several programs execute concur-
    rently, access disk files may be shared among those programs. The communica-
                             to
    tions control program protects againsterroneous resultsthat might be causedby
    c o n f l i c t i n ga c c e s s e s .

    T h e c o m m u n i c a t i o n sc o n t r o l p r o g r a m i s d e s i g n e d o r e a s eo f u s e i n e s t a b l i s h i n g n
                                                                                        f                                                   a
    o r g a n i z a t i o n ' s i r s t c o m m u n i c a t i o n s - b a s es y s t e m ;i t c a n b e r e a d i l y t a i l o r e d t o c o n -
                              f                                               d
    tain only the capabilitiesyou need. The significanceof the servicesit performs is
    indicated by the freedom it offers you in the design,programming, and operation of
    the system. For example:
           Y o u c a n p l a n a n d d e s i g na t e l e c o m m u n i c a t i o n s y s t e mt h a t p e r f o r m s i t s f u n c -
           t i o n s w h e r r r e q u e s t e d y t h o s e w h o n e e dt h e m .
                                                b

           Y o u c a n c r e a t ep r o g r a m si n d i v i d u a l l yt o p e r f o r m t h o s e f u n c t i o n s w i t h o u t b e i n g
           c o n c e r n e da b o u t w h a t o t h e r f u n c t i o n s a r e o c c u r r i n gi n t h e s y s t e mo r w h a t s p e -
           c i fi c t e r m i n a li s i n c o m m u n i c a t i o n i t h y o u r p r o g r a m .
                                                                   w

           Y o u c a n i r r c o r p o r a t e a c ha p p l i c a t i o np r o g r a m i n t o y o u r s y s t e ma s i t i s w r i t t e n
                                              e
           a n d t e s t e d ,w i t h o u t r e c r e a t i n g h e e n t i r e s y s t e m .
                                                               t

      '    Y o u r s y s t e mo p e r a t o r c a n c o n t r o l w h i c h t e r m i n a l sa r e p e r m i t t e d a c c e s so t h e
                                                                                                                               t
           system.

      T h e f o l l o w i n g p a g e s e s c r i b e h e f a c i l i t i e so f f e r e d a s t h e y w o u l d b e v i e w e d b y a n
                                        d              t
      o p e r a t o r a t a t e r m i n a l , b y t h e o p e r a t o ro f t h e s y s t e m ,a n d b y a p r o g r a m m e r .



. . . F R O MT H E V I E W P O I N T F T H E T E R M I N A L O P E R A T O R
                                   O

     T o t h e o p e r a t o r o f a t e r m i n a l , t h e s y s t e m i s a r e s o u r c e o h e l p a c c o m p l i s ht a s k s .
                                                                                                t
     T h e t e r m i n a l o p e r a t o r m a y t h i n k o f t h e s y s t e ma s b e l o n g i n gt o h i m o r h e r a l o n e ,
     u n l e s st h e c o n r b i n e dd e m a n d su p o n t h e s y s t e ma r e g r e a t e n o u g ht o c a u s es o m e
     d e l a y i n i t s r e s p o n s i v e n e s s . l l c o n t e n t i o n a m o n g t e r m i n a l o p e r a t o r sf o r u s e o f
                                                   A
     t h e s y s t e mi s r n a n a g e d y t h e c o m m u n i c a t i o n s o n t r o l p r o g r a m .
                                            b                                       c



How the OperatorRequests Program
                       a

     w h e n a t e r m i n a l i s n o t i n u s e ,i t i s m o n i t o r e d b y t h e c o n t r o l p r o g r a m f o r t h e
     p r e s e n t a t i o n f a r e q u e s t . T h e o p e r a t o r o f a t e r m i n a l c a l l sf o r t h e a p p l i c a t i o n
                           o
     p r o g r a mt o p e r f o r m a s p e c i f c f u n c t i o n b y s i m p l y e n t e r i n gt h e p r o g r a mn a m e a t t h e
                                                    i
     t e r m i n a l . T h e C C P t h e n a t t e r n p t st o l o a d a n d e x e c u t et h e p r o g r a ma n d t o p u t t h a t
     p r o g r a mi n c o m m u n i c a t i o n i t h t h e t e r m i n a lo p e r a t o r . F r o m t h e n u n t i l t h e c o m -
                                                    w
     p l e t i o n o f t h e p r o g r a m ' se x e c u t i o n ,t h e i n t e r a c t i o nb e t w e e nt h e t e r m i n a l o p e r a t o r
     a n d t h e s y s t e n ri s d i c t a t e d b y t h a t p r o g r a m .

    W h e n t h e a p p l i c a t i o np r o g r a m h a s c o m p l e t e de x e c u t i o n ,i t y i e l d s c o n t r o l o f t h e t e r -
    m i n a l t o t h e c o m m u n i c a t i o n sc o n t r o l p r o g r a m - T h e C C P o n c e a g a i nm o n i t o r s t h e
    t e r m i n a l f o r a p r o g r a m r e q u e s t . T h e n e x t r e q u e s tm a y b e f o r t h e s a m e ,o r f o r a
    different, unction.
                      f

    E a c ht e r m i n a l o p e r a t o r m u s t b e t r a i n e d i n t h e f u n c t i o n s h e o r s h e c a n c a l l u p o n
    a n d i n t h e p r o c e d u r e s o r i n t e r a c t i n g i t h t h e a p p l i c a t i o np r o g r a m st h a t p e r f o r m
                                       f                         w
    t h o s ef u n c t i o n s .




                                                                          5
How the Operator                Requests System Services

    while monitoring for program requests,the communications control program can
    also respond to commands to perform servicesfor the terminal.

    T h e o p e r a t o rc a n c o n d i t i o n t h e s y s t e m ' sr e s p o n s e h e n i t i s u n a b l et o c o m p l y
                                                                                    w
    i m m e d i a t e l yw i t h h i s o r h e r r e q u e s tf o r a p r o g r a m . T h e s y s t e mm a y b e t e m p o r a r i l y
    t o o b u s y w i t h r e q u e s t sr o m o t h e r o p e r a t o r s . B y c o m m a n d , h e o r s h em a v c h o o s e
                                        f
    one of the following when this condition occurs:

    o T h e s y s t e ms h o u l d d e n y h i s o r h e r r e q u e s ta n d a l l o w h i m o r
                                                                                                  her to make some
      other request.

    '      T h e s y s t e ms h o u l d h o l d h i s o r h e r r e q u e s ta n d h o n o r i t a t t h e e a r l i e s tp o s s i b l e
           moment.


    Once the operator of a terminal has specified one of these system responses,
                                                                               the CCP
    handlesall program requestsfrom that terminal accordingly until the operator gives
    the other specification.


    A f i l e s p e c i f i c a t i o n o m m a n d a l l o w st h e o p e r a t o r t o s p e c i f y t h e d i s k d a t a f i l e s t h a t
                                      c
    a r e t o b e a c c e s s e d y p r o g r a m sh e o r s h e r e q u e s t s .W i t h i n t h e i n f o r m a t i o n s y s t e m ,
                                     b
    t h e r e m a y b e s e v e r afl i l e s c o n t a r n i n gs i m i l a rd a t a i n t h e s a m ef o r m a t . A s c h o o l
    s y s t e m ,f o r e x a m p l e ,m i g h t h a v e a s e p a r a t e t u d e n t r e c o r d sf i l e f o r e a c h s c h o o l . A n
                                                                             s
    a p p l i c a t i o np r o g r a m r e q u e s t e d y t h e o p e r a t o r m i g h t h a v e b e e n w r i t t e n t o a c c e s s n y
                                                        b                                                                                   a
    o f t h e s ef i l e s , b u t t h e p r o g r a m m u s t b e t o l d w h i c h f i l e t o u s e o n a p a r t i c u l a rr u n . A
    f i l e s p e c i f i c a t i o n o m m a n d i s s u e db y t h e t e r m i n a l o p e r a t o r a p p l i e st o a l l p r o g r a m s
                                    c
    r e q u e s t e d t t h a t t e r m i n a l u n t i l a c o n t r a d i c t o r vc o m m a n d i s i s s u e d .
                       a

        A n o t h e r c o m m a n d p e r m i t s t h e t e r m i n a l o p e r a t o rt o s e n da m e s s a g eo t h e s y s t e m
                                                                                                                t
        operator.

    The commands discussed far are issuedto the communications control program
                                               so
    w h i l e i t i s m o n i t o r i n g a t e r m i n a l f o r r e q u e s t s .O n c e a t e r m i n a l i s i n i n t e r a c t i o nw i t h
    an application program, however, the input from that terminal is meaningful only
    to the application program, with one exception. The CCP checks each message                                                           from
    a terminal to a program for the appearanceof a certain string of characters,specified
    to be significant in your system. When it detects the presenceof these charactersin
    a message,        the CCP interprets the message an attempt by the terminal operator to
                                                                           as
    escapefrom control of the application program and communicate directly with the
    CCP' At this point, the communications control program acceptsa request from the
    operator to cancel the execution of the application program, or to send a message                                                          to
    the system operator. lf the requestwas to send a message,                                        the terminal operator can
    ask the CCP to resumeexecution of the application program after the message sent.                                                    is



[erminalSecurity

    l f y o u a r e c o n c e r n e dw i t h s e c u r i t yo f a c c e s so t h e s y s t e m ,y o u c a n i n d i c a t et h a t a
                                                                            t
    p a s s w o r d e a t u r e b e i n c l u d e di n t h e c o m m u n i c a t i o n s o n t r o l p r o g r a m . T h e v a l i d
                   f                                                                     c
    p a s s w o r d o r t h e c u r r e n t r u n i s e s t a b l i s h e d y t h e s y s t e mo p e r a t o r w h e n h e o r s h e
                   f                                                      b
    s t a r t se x e c u t i o no f t h e c o m m u n i c a t i o n sc o n t r o l p r o g r a m . Y o u m i g h t c h a n g et h a t
    p a s s w o r d n e v e r y r u n , o r r e t a i n i t f o r d a y s o r e v e nw e e k s . I n a n y c a s e ,o n l y
                     o
    o p e r a t o r sw h o k n o w t h e p a s s w o r da r e p e r m i t t e d a c c e s so t h e s y s t e m .
                                                                                          t
      In a system with passwordprotection, no requestsare accepted from a terminal
      u n t i l i t s o p e r a t o rp r e s e n t sh e c u r r e n t p a s s w o r d a n d t h e c o m m u n i c a t i o n s o n t r o l
                                                   t                                  ,                                      c
      p r o g r a mv e r i f i e si t . o n c e a n o p e r a t o rs i g n so n w i t h t h e p a s s w o r d , e o r s h e c a n
                                                                                                               h
      m a k e a n y n u m b e r o f r e q u e s t s i t h o u t r e p e a t i n g t . l f t h e o p e r a t o r i s n o t a l w a y sa t
                                                        w                              i
      h i s o r h e r t e r m i n a l a n d i f o t h e r , p o s s i b l yu n a u t h o r i z e d , e r s o n s o u l d g a i n a c c e s so
                                                                                                   p            c                          t
      t h a t t e r m i n a l ,h e o r s h es h o u l d s i g no f f t h e t e r m i n a l a n y t i m e h e o r s h e l e a v e s t .
                                                                                                                                     i
      W h e n h e o r s h e h a s s i g n e do f f , t h e c o m m u n i c a t i o n s o n t r o l p r o g r a m r e q u i r e s n y
                                                                                             c                                       a
      f u r t h e r u s eo f t h e t e r m i n a l t o b e a c c o m p a n i e d y t h e p a s s w o r d .
                                                                                    b

      Y o u m a y a l s oc o n t r o l a c c e s so t h e s y s t e mb y w r i t i n g y o u r o w n s i g n - o nr o u t r n e .
                                                    t
      T h e o p e r a t o r m u s t p r o v i d e a n y i n f o r m a t i o n r e q u i r e db v t h e r o u t i n e b e f o r e h i s o r
      h e r r e q u e s ti s a c c e p t e d .

     W h e n t h e s y s t e mo p e r a t o r i n i t i a t e se x e c u t i o no f t h e c o m m u n i c a t i o n sc o n t r o l
     p r o g r a m ,t h e C C P a t t e m p t s t o i n f o r m e a c ht e r m i n a l i n t h e s y s t e mt h a t t h e i n f o r -
     m a t i o n s y s t e m i s n o w a v a i l a b l e o r u s e . l f y o u h a v es p e c i f i e dt h a t n o s e c u n t y
                                                          f
     f e a t u r e b e b u i l t i n t o y o u r s y s t e m ,p r o g r a m r e q u e s t s n d o t h e r c o m m a n d sa r e
                                                                                          a
     a c c e p t e d r o m t h e t e r m i n a l a f t e r t h e o p e r a t o r s i g n so n ; h e o r s h e d o e s n o t n e e d
                     f
     t o e n t e r a p a s s w o r co r o t h e r s e c u r i t v i n f o r m a t i o n .
                                         l



. . . F R O MT H E V I E W P O I N T F T H E S Y S T E M P E R A T O R
                                   O                    O

     T h e s y s t e mo p e r a t o r e x e r c i s e si n a l c o n t r o l o v e r t h e c o m m u n i c a t i o n s - b a s es v s t e m .
                                                           f                                                                       d
     H e o r s h e i n i t i a t e si t s a c t i v i t y b y l o a d i n ga n d r u n n i n g t h e c o m m u n i c a t i o n sc o n t r o l
     p r o g r a m . H e o r s h e d e t e r m i n e s h e n t h e s y s t e ms h o u l d r e f u s et o a c c e p tn e w
                                                             w
     r e q u e s t s r o m t e r m i n a l o p e r a t o r s . W h i l e t h e s y s t e m i s i n o p e r a t i o n ,h e o r s h e m a v
                      f
     i n i t i a t ec e r t a i n s y s t e ma c t i o n s ,d e t e r m i n et h e s y s t e m ' s t a t u s ,a n d a l t e r t h e s e t o f
                                                                                                  s
     t e r m i n a l sp e r r n i t t e ctlo a c c e s sh e s y s t e m . H e o r s h e m u s t a l s o m a k e d e c i s i o n s h e n
                                                         t                                                                               w
     e x c e p t i o ns i t u a t i o n s( s u c ha s e r r o r c o n d i t i o n s )a r e d e t e c t e db y t h e c o m m u n i c a t i o n s
     c o n t r o l p r o g r a mo r a p r o g r a m r u n n i n g u n d e r i t s c o n t r o l .


     o n c e t h e c c P h a s b e e ns t a r t e d ,a l l c o m m u n i c a t i o nb e t w e e nt h e c o n t r o l p r o g r a m
     a n d t h e s y s t e mo p e r a t o r i s t h r o u g h m e s s a g ep r i n t e d o n t h e 5 4 7 1 P r i n t e r - K e y b o a r d
                                                                           s
     ( f o r M o d e l s 1 0 a n d 1 2 |,t o r d i s p l a y e do n r h e 3 2 7 7 D i s p l a yS t a t i o n ( f o r M o d e l 1 5 ) .
     S o m e m e s s a g ers Q u i r e e s p o n s e s , h i c h t h e o p e r a t o r k e y s o n t h e a p p r o p r r a t e
                                e        r                 w
     d e v i c e . A t a n y p o i n t d u r i n g t h e e x e c u t i o no f t h e c c p , t h e o p e r a t o r m a y w a n t t o
     c o m m a n d a s y s t e ma c t i o n b y p r e s s i n g h e r e q u e s t( R E O ) k e v o n t h e 5 4 7 1 o r
                                                                  t
     p r o g r a mf u n c t i o n k e y 9 , 10 , o r 1 2 ( p F 9 . p F 1 0 , o r p F 12 ) o n t h e 3 2 7 7 , t h e n k e y i n g
     the command.



                           Control program
Initiatingthe Communications

     w h e n h e o r s h e s t a r t st h e e x e c u t i o n o f t h e c o m m u n l c a t i o n s o n t r o l p r o g r a m ,t n e
                                                                                                     c
     o p e r a t o rc a n e x e r c i s e e r t a i n o p t i o n s . F o r e x a m p l e ,h e o r s h e c a n :
                                        c

         Specify the system password to be used during this run.

         Preventaccess certain disk data files that are normally accessible programs
                                 tcl                                                                                  to
         r u n n i n g u n d e r c o n t r o l o f t h e c o m m u n i c a t i o n s o n t r o l p r o g r a m ;f o r e x a m p l e ,t h e
                                                                                    c
         file may not be built everyday.

         Prohibit the requestingof certain application programs that are normally part of
         the information system.
        o Specify the set of terminals that can have access the information system at the
                                                          to
          time the system beginsits activity.

        .   Causea serviceaid program to be included in the communications control oro-
            gram if a malfunction in its operation is suspected.



    SystemOperatorCommands


        During
             operation thecommunications
                     of                     program, system
                                      control      the    operator
                                                                 can
       c o m m a n dt h e C C p t o :


        o   Disableor enable access the system by any terminal.
                                   to

        '   Changethe terminal which will actually be addressed a program when that
                                                               by
            program attempts to access terminal by name.
                                      a

       o    Initiate the online test of a terminal to determine whether it is operating
                                                                                        correctly.

       o    I n i t i a t et h e e x e c u t i o no f a n a p p l i c a t i o np r o g r a m .


       o C a n c e lt h e e x e c u t i o n o f a n a p p l i c a t i o np r o g r a mc u r r e n t l y r u n n i n g .

       o    Display information about the system,sstatus (seenote).

       o Accept no new program requestsfrom terminars and notify
                                                                 the system oper-
         ator when all outstanding requestshave been satisfied.

       '    Cease activity of the system immediately and terminate execution of the
                 all
            CCP.


I      r    O p e n a n d c l o s ed i s k f i l e s .

       y'y'ote.-
              some of the information about system status that may be displayed is:

       o The identification of terminals currently permitted access the system.
                                                                  to

       .    The complete status of any specific terminal in the system.


       o The identification of programs currently executing, which terminal each is serv-
         ing, and which program is currently in control of the central processingunit.




    Messages

       The system operator can receive messages
                                              from the communications control pro-
       gram or from an application program. The CCP prefixes each message
                                                                        with the
       identification of the program that issuedit. Messages  which require a reply from
       the operator are further prefixed with the indication that a reply is required.
        Among the messages the system operator which require reply are halt codes. In
                            to
        a system with severalapplication programs operating concurrently. a halt issuedfor
        one program causesonly that program to suspendoperations until a responseis
        supplied. The communications control program and other application programs
        under its control continue to operate.



. . . F R O M H EV I E W P O I NO F T H EP R O G R A M M E R
             T                  T

        T h e c o m m u n i c a t i o n s o n t r o l p r o g r a m a i d st h e p r o g r a m m e ri n t w o p r i m a r y w a y s :
                                         c

        a    R e l i e v e s a n y p r o g r a m m i n gc o n c e r n si n h e r e n t i n a n e v e n t - d r i v e n y s r e m ;
                            m                                                                                             s
            t h e r e f o r ea l l o w s c o n c e n t r a t i o no n a p p l i c a t i o np r o g r a m st h a t s o l v et h e p r o b l e m s
            of his or her orqanrzation.

        o   P e r m i t sw r i t i n g a p p l i c a t i o np r o g r a m st h a t i n c l u d ec o m m u n i c a t i o n si n p u t /
            o u t p u t i n a h i g h - l e ' , r ea n g u a g e .
                                                  ll

    Programsthat run under the communication control program can be written in any
    of four languages:

    .       R P GI I

    O COBOL

    .       FORTRANIV

    .       BasicAssembler

     B y w r i t i n g i n R P G l l , c o B o L , o r F o R T R A N , y o u c a n a v o i dt h e s t r i c t r u r e s
     r e q u i r e dw h e n u s i n g B a s i cA s s e m b l e rL a n g u a g e .


    Although your program may have to contend with others for system resources,
    y o u c a n i g n o r et h e p r o b l e m st h a t a r i s ef r o m t h i s . T h o s e p r o b l e m s
                                                                                                              aremanaged
    b y t h e c o n t r o l p r o g r a m . Y o u a r e a s s u r e d h a t a l l r e q u i r e dr e s o u r c e s r e a v a i l a b l e
                                                                      t                                          a
    t o y o u r p r o g r a m e a c h t i m e i t i s e x e c u t e d . l f n e c e s s a r yt,h e c c p d e f e r st h e
    e x e c u t i o no f y o u r p r o g r a m u n t i l t h o s e r e s o u r c e s r e a v a i l a b l e . l f y o u r p r o g r a m
                                                                                       a
    s h a r e s c c e s so a d i s k d a t a f i l e w i t h a n o t h e r c o n c u r r e n t l ye x e c u t i n gp r o g r a m ,t h e
               a          t
    c c P m a n a g e sh e c o n t e n t i o n a n d d o e s n o t p e r m i t t h e t w o p r o g r a m st o c a u s ea n
                            t
    e r r o n e o u sr e c o r d u p d a t e t h r o u g h c o n f l i c t i n g r e a d sa n d w r i t e s .


    Programsthat execute under the control of the communications control program are
    written much the same as programs in the same languagefor a system without tele-
    communications. That is, the statementsused to processdata and the handling of
    data files are identical. The standard disk data management methods are supported
    by the control program. Only two elements are likely to differ significantly:

    o The overall design of the program.

    o The statementsused to communicate with terminals or with the system operator.
ProgramDesign

       lf you currently use a data processingsystem without telecommunications. many
       programs in your system operate upon a long seriesof transactions- hundreds or
       perhapsthousands. The data from those transactionsprobably updates a single
       disk file. Once started, such a program processes the transactions before it is
                                                         all
       finished. of course, the transactionsrepresentedby the data actually happened
       earlier in the day, week, or month. The data is collected into a batch before it is
       used to update the files of the system. When they have been updated, the files
       contain information reflecting the state of your organization'saffairs as of the last
       transaction in the batch.

       It is also possibleto design programs that use the batch processingmethod to advan-
       tage in a communications-based    system. lf a terminal is located where transactions
       are occurring and if data is entered regardingthe transactionsas they occur, the
       system can reflect the current status of your organization.

    Batch processingrequiresthat the terminal be dedicated to input of one kind, or
    severalclosely related kinds, of transaction data. Frequently, however, during a
    p e r i o d o f t i m e , a t e r m i n a l i s u s e dt o i n q u i r e i n t o i n f o r m a t i o n c o n t a i n e d i n a n u m b e r
    of files, or to enter data concerning transactionsof many different types affecting
    severaldifferent files. In these cases,it is unlikely that the terminal would be served
    for any length of time by a single program. In fact, each program may be written to
    p r o c e s s o m p l e t e l y o n l y a s i n g l et r a n s a c t i o no r i n q u i r y f r o m t h e t e r m i n a l , t h e n t e r -
                 c
    m i n a t e i m m e d i a t e l y . I n p r a c t i c e ,t h e m a j o r i t y o f a p p l i c a t i o n s f t e l e c o m m u n i c a t i o n s
                                                                                                              o
    involve this kind of processing,therefore, programs are required to update all files
    affected by a transaction, but handle only a single transaction per execution. This
    certainly implies a program design different from that for a batch-oriented svstem.



TerminalInput/Output

    T h e s e c o n ds i g n i f i c a n td i f f e r e n c ei n p r o g r a m m i n gu n d e r t h e c o m m u n i c a t i o n sc o n t r o l
    p r o g r a m i s t h e m a n n e r o f p r o g r a m m i n gf o r c o m m u n i c a t i o n w i t h a t e r m i n a l a n d t h e
    system operator.

    T h e M L T A l O C S a n d B S C A I O C S f a c i l i t i e sa r e n o t d i r e c t l y a c c e s s i b l e y h i g h - l e v e l
                                                                                                                   b
    p r o g r a m m i n gl a n g u a g e s . h e c o m m u n i c a t i o n sc o n t r o l p r o g r a m i n c o r p o r a t e s L T A
                                           T                                                                                  M
   I O C S o r B S C A I O C S ( o r b o t h . i f y o u h a v eb o t h l i n e t y p e s i n y o u r s y s t e m ) a n d
   o f f e r s t h e a p p l i c a t i o np r o g r a m m e ra m e t h o d o f u s i n gt h e s e I O C S f a c i l i t i e st o i n t e r -
   act with terminals.

   Since there are no statements in the languages specify terminal actions, the appli-
                                                  to
   cation program indicates those actions to the communications control program by
   means of one of the following statements.each of which causesa Drancn to a sup-
   plied subroutine:

   .     In COBOL or FORTRAN - CALL statement

   o     I n R P G l l - E X I T s t a t e m e n t ,o r u s e o f a S P E C I A L f i l e

   .                                  -
         I n B a s i cA s s e m b l e r b r a n c h i n s t r u c t i o n

   Each of these statements is accompanied by parametersto indicate the specificsfor
   the operation.



                                                                     10
             Those specificsinclude the following information necessary
                                                                       to control the terminal
             action requested:

             o The operation desired.


          o The length of the message be sent, or
                                    to            the maximum rength of a message be
                                                                                to
            received.


         '       T h e n a m e o f t h e t e r m i n a l w i t h w h i c h t h i s c o m m u n i c a t i o ni s t o t a k e p l a c e .

         r       The area in main storagewhich contains the message be sent, or should contain
                                                                  to
                 a messageto be received.

             S o m e o p e r a t i o n st h a t c a n b e s p e c i f i e da r e :

         a       Read a messaqe

         o Write a messaoe

         .      Write a message
                              and wait for a reply

         o       Release
                       the terminal from any further use in this program

         Previousdiscussionmay have implied that an application program communicates
         only with the terminal that requestedit. In fact, most communication by programs
         r u n n i n g u n d e r t h e C C P i s w i t h t h e r e q u e s t i n g e r m i n a l . B u t t h e a b i l i t y a l s o e x i s t st o
                                                                                    t
         addressother terminals. A terminal is addressedin the program by a name that is
         chosen by the user; the name normally appliesto one particular terminal. However,
         s h o u l d a c e r t a i nt e r m i n a l b e c o m e u n a v a i l a b l e u r i n g a r u n o f t h e c o m m u n i c a t i o n s
                                                                                    d
         control program, the system operator can reassign                                   the name to another terminal.
         Any program addressing terminal by the reassigned
                                                  a                                              name addresses           the new termi-
         nal. For the most part, the application program need not be concerned with the
         type of terminalwith which it is communicatino.

         w h e n a S y s t e m / 3 M o d e l 1 0 o r M o d e l 1 2 i s u s e d ,a n a p p l i c a t i o np r o q r a mc o m m u n -
1
         i c a t e sw i t h t h e s y s t e mo p e r a t o r b y a d d r e s s i n gh e 5 4 7 1 p r i n t e r / K e v b o a r d
                                                                                   t                                           as
         a n o t h e rt e r m i n a l . T h e n a m e C O N S O L i s a l w a y s u s e dt o a d d r e s s h e 5 4 7 1 . W h e n
                                                                                                                t
         a s y s t e m / 3 M o d e l 1 5 i s u s e d ,a n a p p r i c a t i o np r o g r a mc o m m u n i c a t e s i t h t h e
                                                                                                                      w
         s y s t e mo p e r a t o r b y u s i n gt h e s t a n d a r dM o d e l 1 5 c o n s o l ei n t e r f a c eo r b y a d d r e s s i n g
         t h e t e r m i n a l n a m e C O N S O L . T h e o n l y o p e r a t i o n sa v a i l a b l e o t h e a p p l i c a t i o n
                                                                                                        t
         p r o g r a mw h e n i t i s c o m m u n i c a t i n gw i t h t h e s y s t e mo p e r a t o r
                                                                                                          are:

         o Write a messaoe

         o Write a message nd wait for a reply
                         a



    H O WC A N T H EC C PB E T A I L O R E D O M Y N E E D S ?
                                            T
        The communications control program feature of disk system management,like disk
        system managementitself. can be tailored to suit your processingrequirements.

        when you receivethe communications control program, you must first generatea
        disk system for your installation if you have not already done so. At that point,
        you are ready to tailor a communications control program according to number
                                                                                a
        of options you selecr.

                                                                           11
                        Control program
Generating Communications
         the

    T h e c o m m u n i c a t i o n s o n t r o l p r o g r a mi s a h i g h l y m o d u l a r p r o g r a md e s i g n e d o y o u
                                         c                                                                                      s
    c a n i n c l u d e f u n c t i o n s y o u r e q u i r ea h d e x c l u d e t h o s e o f n o v a l u e t o y o u r i n s t a l l a t i o n .
    The processof selectingfunctions you want is known asgeneratingthe control pro-
    gram.


    The processinvolves:


    L   C r e a t i n ga s e t o f c o n t r o l r o u t i n e sw h o s e s p e c i f i cc o n t e n t m a y b e a b s o l u t e l yu n i q u e
        to your installation.

    2 . J o i n i n g t h e s er o u t i n e sb y a l i n k a g ee d i t p r o c e s s .

         C o p y i n g a p p r o p r i a t ea d d i t i o n a ls u p p o r t i n gr o u t i n e s .

   The output of the generation processis a set of object modules and subroutines on
   a d i s k p a c k s p e c i f i e db y y o u . T h i s o u t p u t i s y o u r v e r s i o no f t h e c o m m u n i c a t i o n s
   control program. lt includes the program to be loaded and run each time the svs-
   t e m o p e r a t o r i n i t i a t e sy o u r c o m m u n i c a t i o n 



◦ Jabse Service Manual Search 2024 ◦ Jabse PravopisonTap.bg ◦ Other service manual resources online : FixyaeServiceinfo