O S - 8

                             Prepared by:

                              Rick Moore



       This  is  a  reference  document  for  Field  Service  use   in

diagnosing system problems. The information presented in this  chapter

is extracted from various OS-8 reference manuals and literature  which

are listed in the appendix.

       It is not intended to be a course on OS-8 or a  substitute  for

standard DEC software manuals. However, the topics presented here  are

some of the more commonly used features and some of the commands  that

should help you to better serve  your  customer  through  an  enhanced

knowledge of his OS-8 operating system.

       It is strongly recommended that you be extremely careful  using

your customer's software as a little knowledge is a  dangerous  thing.

If you do work on a customer's files, be sure to  use  copies  of  his

system only. Tell him what you feel the problem is and  let  him  take

any corrective action.

       OS-8 consists of an executive and library  of  system  programs
which reside on a mass storage device called a "system  device".  This
could be a disk, dectape or floppy unit. The executive supervises  the
overall program processing and consists of the  following  four  major

               - Keyboard monitor      ( KMON )
               - Command Decoder       ( CD )
               - Device Handlers
               - User Service Routine  ( USR )

       The Keyboard Monitor provides communications between  the  user
and the OS-8 Executive.  The  root  segment  of  the  monitor  resides
perminently in memory  and  occupies  256  words.  Commands  from  the
console terminal are interperted  and  whenever  needed,  the  Command
Decoder, USR, KMON, and ODT are brought into memory  in  a  series  of
overlays while the contents of the memory used is swapped out  to  the
system scratch area. In this manner it is possible to run  a  baseline
system in only 8K words of memory.

       The commands that are executed directly from the KMON are:

       ASsign      -    assigns a new, user defined device name  to  a
                        perminant device.

       DEASsign    -    restores perminant  device names

       GET         -    loads core image  files  into  memory  from  a

       START       -    starts  execution  of  a  program  already  in

       RUn         -    loads core image (.SV) files into memory  from
                        a device and starts execution

       R           -    loads core image (.SV) files into memory  from
                        the SYStem device and starts execution

       SAve        -    creates core image programs on a device

       ODt         -    invokes the Octal Debugging Technique

       DAte        -    sets / prints the system date
       The Command Decoder is  called  when  a  system  program  needs
additional information from the operator concerning files to be  acted
upon or devices to be used. You are in the  Command  Decoder  whenever
the prompt character "*" is issued.

       Understanding the Command Decoder line format is  probably  the
most important step to successful usage of the OS-8 Operating  System.
It is as follows:


... to translate ...

       OUTDEV:     -    the output device     (SYS:,RKB0:,DTA0:,LPT:)
       OUTFIL.EX   -    the name of the output file and it's extension

       INDEV:      -    the input device
       INFILE.EX   -    the name of the input file and the extension

       SW?         -    an optional switch  ...   differint  for  each
       =N          -    numerical  value   (ie:   in  direct  =N#   of

       There may be 0-3 input files,  0-9  output  files,  0-3  option
switches, depending on the requirements of the individual program.  In
several programs, it is not necessary  to  specify  every  detail  ...
certain programs have default values for devices, switches, etc.   The
only way to be sure of this is to know the  program  you  are  working

       Again, the value of learning the command decoder format  cannot
be overstressed ... the  same  basic  format  is  used  thoughout  DEC
software.  (ie: RT-11, RSTS, etc.)

       Device Handlers are subroutines which handle data  transfer  to
and from peripheral  devices.   Device  handlers  for  the  particular
hardware system you are using are activated by  the  program  "BUILD".
These subroutines are then available to  all  OS-8  programs.   It  is
through  the  use  of  device  handlers  that  a   sort   of   "device
independence" is acheived.

       The USR is a collection of subroutines that perform  operations
of  opening  and  closing  files,  loading  device  handlers,  program
chaining, and calling the CD. The USR  provides  these  functions  not
only for the system itself, but for any programs running under OS-8.

       Mount the OS-8 System on the appropriate hardware  and  execute
the bootstrap. This may be as simple as pressing a  "BOOT"  button  or
require a toggle-in  program  from  the  operator's  console.  Various
bootstraps are listed in the appendix.

       After the bootstrap is executed, the monitor will print  a  dot
"." on the console. At this point, KMON is active and  the  system  is
ready to accept one of the monitor level commands listed on page 1.


       The Concise Command Language ia a means of providing an easy to
understand "English-like" command interface between the  operator  and
the monitor. It translates the commands,  chains  to  the  appropriate
system programs, passes arguments and filespecs, and starts execution.
Any CCL command can be simulated by typing the necessary  monitor  and
CD responses manually. For example:

      .DIR                 is equivalent to      .R DIRECT

      .COPY RXA1:<RKA0:    is equivalent to      .R FOTP

       The use of CCL is optional in OS-8; manditory in OS-78. This is
because you cannot normally access monitor level  commands  in  OS-78.
There is a way around this; by typing ".SET SYS OS8" it is possible to
turn on this attribute.


       .DIR            - types  directory  of  system  device  on  the
       .DIR-L          - prints directory of  system  device  on  line
       .DIR RKB0:-L    - prints  directory  of  device  RKB0  on  line


       The program "SET.SV" is called by the ".SET"  CCL  command  and
can be used to modify some of the attributes  of  the  various  device
handlers. Some useful ones are:

       .SET SYS  OS8            - allows  monitor  level  commands  in

       .SET SYS OS78           - normal OS-78 mode; CCL commands only

       .SET SYS INIT           - causes the command file "INIT.CM"  to
                                 be executed upon boot-up.

       .SET SYS INIT  [cmd]     -  causes  the  command  [cmd]  to  be
                                 executed upon boot-up.

       .SET SYS NO INIT        - negates the above

       .SET LPT LA78           - allows PDP-8A (M8316) parrallel  port
                                 as  controller  for  LA-180   (device

       .SET LPT LA8A           - restores LPT to  normal  0660  device

       .SET TTY SCOPE          - causes a rubout to actually erase the
                                 character from the screen.

       .SET  TTY  NO  SCOPE       - causes  the  rubout  to  echo  the
                                 character/slash    combination    for
                                 hardcopy terminals.

       .SET TTY PAUSE          - causes the terminal  to  pause  every
                                 "height" lines for ease of reading.

       .SET TTY HEIGHT 24      - tells the handler the screen  has  24

       .SET TTY WIDTH 80       - allows 80  character  width  to  VT52

                          ***  WARNING   ***

       The command ".SET SYS NO INIT" must be given before  attempting
to use the "BUILD" program, since execution of the "INIT.CM"  file  or
any CCL command will cause the previous contents  of  memory  and  the
system scratch  area  to  be  altered.  Also,  since  the  process  of
executing this file may entail several overlays, the usefullness of it
on any media except disks or diskettes is questionable.

       There are three standard types of OS-8  file  formats  used  by
OS-8 and associated system programs;  ASCII,  Binary  and  Core  Image

       ASCII and Binary files are packed three characters to every two
12 bit words as follows:

               |               |                               |
Word 1         |  Char. 3      |       Character  1            |
               | (bits 0-3)    |        (bits 0-7)             |
               |               |                               |
               |               |                               |
Word 2         |  Char. 3      |       Character  2            |
               | (bits (4-7)   |        (bits 0-7)             |
               |               |                               |
                    0 - 3                  4 - 11

       In Binary files, the binary data must be  preceded  by  one  or
more frames  of  leader/trailer  code  (ASCII  200  code).  The  first
character must be either 100-177 octal (origin  setting  for  absolute
binary  files),  240-257  octal  (a  COMMON  declaration   frame   for
relocatable binary files), or 300 octal which is  an  origin  setting.
The end of binary data is one or more frames of leader  trailer  code.
ASCII and Binary files are terminated by a CTRL/Z code (ACSII 232).

       A Core Image file consists of a header followed by  the  actual
core image. The header is called the  Core  Control  Block  (CCB).  It
consists of first 128 words of the first  block  (256  words)  of  the
file. The CCB is a table of information that contains  the  length  of
the file, the program's starting address,  and  the  Job  Status  Word
(JSW). The CCB for a program at the time it is  loaded  into  core  is
always saved in words 200-377 (octal)  of block  37  on  the  system's
scratch area. It is placed there by the GET or RUN  operations  or  by
the ABSLDR program. This information is then used  when  performing  a
SAVE without arguments.

       Files are referenced symbolically  by  a  name  of  up  to  six
characters followed, optionally, by  a  period  and  a  two  character
extension. The extension to a file name is generally used to type  the
files according to their formats  or  defaults  to  particular  system

       In most cases, the user will want to conform  to  the  standard
file name extensions established for OS-8. If  the  extension  is  not
specified for a files, some system programs  will  append  an  assumed
extension by default. This  default  extension  can  be  overidden  by
stating the extension in the CD line explicedly.

       The most common OS-8 standard default extensions are:

               SV      - core image programs

               BN      - binary programs

               PA      - PAL8 assembly language sources

               BA      - BASIC source files

               BI      - BATCH control files

               SY      - system heads

               DG      - diagnostic program                    **

               BX      - DECX8 exercisor modules               **

               X8      - customised DECX8 system exercisor     **

       **      refers to psuedo standards imposed by the New England
               District PDP-8 Diagnostic System.

       Files can be transfered between OS-8 devices  by  using  either
"FOTP.SV" (File Oriented Transfer  Program)  or  "PIP.SV"  (Peripheral
Interchange Program)  or  the  CCL  commands  that  call  them.  These
commands and their uses are:

       COPy            - copies files from one device to another
       DELete          - deletes files from a device
       LIst            - lists an ASCII files on the LPT
       REName          - changes the name of a file in the directory
       SQuish          - eliminates all empty and deleted files  on  a
       TYpe            - types an ASCII file on the console terminal
       ZERO            - zeroes the directory of  a  device,  deleting
                         all existing files on that device

       For example, to copy file FOO.PA from RXA1: to RKB0:

               .COPY RKB0:<RXA1:FOO.PA

       ( note the similiarity between this and the format of
         the Command Decoder Line on page 2.)

       To copy an entire device using PIP and FOTP type:

       .R PIP                          first transfer the system heads

       .R FOTP                         now all the files
       *RKA1:<RKA0:*.*                 using wildcard transfers

       For floppies, it is easier since the program "RXCOPY.SV" or the
CCL command ".DUPLicate" will copy the entire device.

       The  "/Y"  option  of  PIP.SV  can  be  used  for  system  head
manipulation. A system head is 50 blocks long and is  located  at  the
beginning of the system device. It contains the system bootstrap,  the
monitor, and all it's overlays. System heads are sometimes  stored  as
files on a device for ease of use with the extension ".SY".

       To move a system head:

       .R PIP

       if "RKA1" is a virgin device,  a  skeleton  directory  must  be
created, so type:



       Certain   commands   allow   wildcards   in   the   file   name
specifications. These commands are COPY, DELETE, DIRECT, LIST, RENAME,
and TYPE.

       Wildcards allow a filename or extension to be totally  replaced
with an asterisk (*) or partially repalced with a  question mark  (?).
Wildcards are particularly useful when doing multiple file  transfers.
This is illustrated in the following examples:

       TEST1.*         - all  files  with  the  name  TEST1  and   any
       *.BN            - all files with a BN extension and any name
       *.*             - all files with any name and any extension
       TEST2.B?        -  all  files  with  the  name  TEST2  and  any
                         extension starting with a B
       TES??.PA        - all files with a PA extension  and  any  name
                         from 3 to 5 characters beginning with TES

       the asterisk amd question mark can be used together

       ???.*           - all files with any extension  and  with  file
                         names of three characters or less

       The program "BUILD.SV" is  the system  generation  program  for
OS-8 which allows the user to:

       1.  Maintain and update device handlers  in  an  existing  OS-8

       2.  Add device handlers to a new or existing system.

       3.  Change  the  system  characteristics  to  reflect  hardware

       Device handlers are supplied with the OS-8 system  and  are  in
the format of Binary (.BN) files.

       To run the Build program, type:

               .RUN SYS BUILD


           It is important that the user specify  the  "RUN"  command,
           rather than the "R" command when loading BUILD  into  core.
           This will allow the CCB to be stored on the system  scratch
           area for use with the SAVE command!

           Also, since the system scratch area is used at  times  when
           the "INIT.CM" file is executed, it is imperative  that  the
           command ".SET SYS NO INIT" be given prior to beginning  the
           BUILD process. After the program is SAVEd, ".SET SYS  INIT"
           can be reinstituted.

           This matter cannot be  overemphisized  ...  SAving  "BUILD"
           without these precautions  will  appear  to  work  and  the
           system will boot without failure, however,  the  next  time
           BUILD is run, it will not work! This is because the  proper
           CCB parameters will have been lost.


       Changing a system's parameters can be a  complicated  procedure
with too many variables to be explained in this document. For complete
instructions on BUILD, see the appropriated OS-8 Manual.


       Some of the devices that are available in the OS-8 system are:

               SYS:    -       the system device
               DSK:    -       the default device (usually SYS:)
               RKA0:   -       "A" side of RK05 drive #0
               RKB0:   -       "B" side of RK05 drive #0
               TTY:    -       console teletype
               LPT:    -       line printer
               LQP:    -       letter quality printer (Diablo)
               PTR:    -       paper tape reader
               PTP:    -       paper tape punch
               DTA0:   -       dectape drive #0
               DTA1:   -       dectape drive #1
               RXA0:   -       RX01 floppy drive #0
               RXA1:   -       RX01 floppy drive #1
               RL0A:   -       RL01 area "A" drive 0
               RL0B:   -       RL01 area "B" drive 0
               RL0C:   -       RL01 area "C" drive 0


       The OS-8 File UTILity program was orginally  developed  by  Jim
Crapuchettes of Menlo Computer Associate,Inc., Menlo Park, CA.  It  is
now included within the OS-8 Extension Kit after release V3D,  and  is
also contained on the New England  District  PDP-8  Diagnostic  System
after release V8.04.

       FUTIL enables a user to examine and modify the contents of mass
storage devices,  including the SYStem device,  and  is  therefore  as
dangerous as it is useful! It can be used to  recover  damaged  files,
repair destroyed directories,  patch  programs  on  the  mass  storage
device, and check for bad blocks on the device.

       It is this last feature that is particularly useful  to  us  in
Field Service as we often have questions concerning the validity of  a
customer's disk or diskette. The following procedure can verify this:

       .R FUTIL

       SET DEVICE RXA0                 floppy drive 0  is  the  target

       SCAN 0-755                      scans the 756 (octal) blocks on
                                       the device

       EXIT                            returns to OS-8

       If any bad blocks were encountered, the program would report

               BAD BLOCK nnn           where "nnn" was faulty

       The cause of this could be due to either a  bad  CRC  character
due to blown data (can be recopied) or blown format  (device  must  be
reformatted). In the case of floppies, the later condition is fatal as
they cannot be reformatted.
       FUTIL can be used to scan devices regardless of  their  program
contents, for example, OS-8, COS 300, or  any  customer  written  file
structure can be scanned, as long as standard sector format is used.

       to SCAN an RK05 Disk:

       .R FUTIL

       SET DEVICE RKA0                 or RKA1, etc.

       SCAN 0-6257                     there are 6260 blocks

       SET DEVICE RKB0                 now the other side

       SCAN 0-6257




               At this time, a note on the "sides" of  a  disk  is  in
               order. The RK05 is  broken  up  into  two  (2)  logical
               devices called "RKA0" and "RKB0" as the RL01 is  broken
               into three (3) devices called "RL0A", RL0B", and "RL0C"
               by OS-8. This is because of the system's  inability  to
               address the entire  disk  and  the  limited  number  of
               entries the directories can hold.

               These "sides" are actually not physical sides (who ever
               heard of a three sided RL01), but refer (on  the  RK05)
               to the first 6260 sectors as "RKA0" and  the  remaining
               6260 sectors as "RKB0". A look at  the  hardware  shows
               that after the sector counter overflows (at 16 sectors)
               the heads switch to the other surface. After the sector
               counter overflows again, the heads switch back and then
               the cylinder address increments. Thus RKA0  is  on  the
               outer tracks of the disk  and  RKB0  is  on  the  inner


Feel free to contact me, David Gesswein with any questions, comments on the web site, or if you have related equipment, documentation, software etc. you are willing to part with.  I am interested in anything PDP-8 related, computers, peripherals used with them, DEC or third party, or documentation. 

PDP-8 Home Page   PDP-8 Site Map   PDP-8 Site Search

Mirror site if this site is slow