AUSAM/doc/intro.agsm/doc1

.ds T A Guide To Using UNIX
.SH "Introduction to Computers"
.P
A computer is a machine that can
perform calculations
and manipulate words and sentences.
Instructions tell the computer what to do,
what formula to use to perform a calculation
or how to interpret and alter
other symbols being sent to it.
A computer is a powerful tool because it can process symbols
and follow instructions very quickly.
It is,
however,
very simple\-minded
for it can only follow
a predetermined set of instructions.
A computer cannot process any information
that is different from what it was instructed to expect.
.H 2 "What Is a Program?"
.P
.IX Program
A program is simply a set of instructions which
tells the computer
how to process symbols that are being sent to it or how to
reprocess symbols already stored inside it.
A program is "run" when the computer executes the instructions.
A
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user
(anyone who uses a computer) may write a program if he knows
what symbols to use to make the computer understand his instructions.
Or he may run a program written by someone else.
In this case,
he must know how to tell the computer to run the
particular program and he must know
how to give information to the program,
if necessary, so that the program can do the particular
task desired by the user.
.H 2 "What is a Time\-sharing System?"
.IX Time\-sharing
.IX System
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Time\-sharing is a process by which a computer "shares its time"
among many activities.
It will follow a user's instructions for a while,
and then
do what a second user is telling it to do,
and then a third, and so on.
When it has given each of the users some of its time,
it goes back
and works for the first user again,
and so on.
All this time\-sharing is usually so fast that it appears to
each user that the computer is working only for him.
The computer follows a set of instructions
which tells it how to share
time and how to respond to instructions received from each user.
The computer, acting under these time\-sharing instructions, is referred
to as "the system".
The AGSM computer operates under
the UNIX time\-sharing system,
developed by Bell Labs.
.H 2 "Computer Memory"
.IX Memory
.IX Core
.IX Disk
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UNIX supports two different types of memory.
It has a big storage area on a device called a "disk".
On the disk are stored programs and any information
or data which
needs to be kept on the computer over a period of time.
The other type of memory is called "core".
Computers use core as a working area
to store instructions that they
are executing and information that they are processing.
When a program is used, it is first copied from the
disk to core so it can be run.
.IX Files
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To keep the information on the disk in order, it is organized into
units called "files".  A file may contain a specific set of data,
or it may contain the instructions in a program,
or it may even be empty.
To run programs which require a lot of data,
especially statistical programs,
it is often better for the
user to enter his data into a file before he runs the program.
.IX Terminals
.H 2 "About Terminals"
The terminals connected to the computer allow each user to
interact with the system.
The user gives commands to the system by typing at a
terminal.
The system can also output information on the terminal
for the user to see.
By typing the right commands at the terminal, the user can
tell the system to run a program.
The program may contain instructions which
tell the system to
perform calculations,
print information on the user's terminal
or to wait for the
user to type in some characters.
At any time the user may stop the program
which is running
and give the system a new command.
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There are four main types of terminals
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video terminals.
These terminals display their information on a small television screen.
AGSM currently uses two different brands of video terminals, the TELERAY
and the VC\-404.
The place where the next character will be printed is indicated by
the cursor which looks like a large underscore on the TELERAY
and a flashing box on the VC-404.
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The TELERAY has a number of switches and they should be set to
(listed from the top)
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SOD
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NARROW
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HIGH
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REMOTE
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FULL
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The VD\-404 has even more switches to set.
The two switches on the back of the terminal should be set to
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not TRANSPARENT (i.e. TRANSPARENT off)
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EVEN PARITY
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The switches on the keyboard should be set to (from the top)
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ANY (this switch is unused)
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APL (out)
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PAGE (out)
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FULL (in)
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LOCAL (out)
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Most of the time the switches on both kinds of terminals will be correct.
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graphics terminals.
These terminals are designed for use in drawing and displaying graphs and
drawings.
They may be used for normal typing but are not as easy to use as video
terminals.
AGSM has only one brand of graphics terminals, TEKTRONIX.
One of its features which makes it hard to use is that it only prints
in upper case but the system converts characters into lower case as you type
them in.
These terminals are very expensive and must be treated carefully.
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Firstly, and most importantly, you must not allow characters to be printed on top
of one another. This doesn't happen on video terminals because as each
line is printed, the previous lines 'scroll' up the screen.
On the TEKTRONIX, they simply go to the top of the screen and overprint
on a previous line.
The screen can be cleared by depressing the 'page' key (top right corner).
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Secondly, when the terminal is switched on, the screen glows a bright green.
This is normal and indicates that the screen is ready to use.
You must however clear the screen by using the 'page' key as above in
order to use it.
This should be done as soon as possible
as otherwise damage may result.
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hard copy terminals.
These terminals actually print their output onto paper.
AGSM uses only one brand of hard copy terminal but there are two models in use.
One is called a DECwriter
and it has a number of switches, all of which should be in the UP position
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except
for the one labelled 300, which should be down.
The other model is called an LS\-120 and is essentially the same as a
DECwriter but four times faster.
The switches are set in the same way as the DECwriter.
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From time to time the hard copy terminals need to be fed
some paper.
This paper is normally used paper\*F lying on tables in the back of
.FS
this paper does not grow on trees.
It comes from people who donate their used printouts for recycling.
Please follow suit.
.FE
room 422.
This paper is used on one side but this doesn't matter if you use the other side.
If there is no paper left, or if you wish to make a special printout for
an assignment, ask the computer personnel for some new paper.
The way to feed some paper to a DECwriter is
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turn it off (the power switch is in the upper left corner)
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lift up the lid (most easily done by pulling up on the clear plastic cover)
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opening the tractors (these are the metal clips that hold the paper onto
the spikes that pull the paper up)
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poke the new paper upwards through the (there is only one) narrow slit
under the tractors
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align the holes in the side of the paper with the spikes in the tractors
and shut them (this is best done one side at a time)
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roll the paper upwards 20 cms or so (by twisting the black plastic knobs on the side of
terminal)
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feed this paper through the gap between the lid and the clear plastic guard
and shut the lid
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turn the power switch back on
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Wasn't that fun !!!
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The LS-120 is similar; the only differences are at the start
that you should
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not
turn off the power
and that when you have loaded the paper, instead of turning the machine back on, you
should depress the key marked 'ESC' and then the key with '0' and ')' on it.
The LS\-120 will then continue printing without losing any characters.
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high quality terminals.
These terminals produce high quality printout slightly superior to that of a typewriter.
AGSM has one such terminal and it is known as the QUME.
The QUME is not available for general use
and use of the QUME has to be booked ahead in the book in Rm 436.
Large outputs (say three hours printing time or more) need to get approval
from system staff before the booking can be made.
Due to previous bookings and the possibility of machine breakdown, any
document to be printed on the QUME should be ready about a week before it is
due\*F.
.FS
you have been warned!
.FE
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.H 2 "When Can You Use The Computer?"
The AGSM computer is open for use
between 8:00am and 10:00pm weekdays for
the students and staff of the AGSM.
Anything outside these times comes
under the jurisdiction of the university,
hence if you wish to use the machine
on weekends,
or after 10:00pm,
you should contact
system staff
for the appropriate passes.
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Occasionally, the computer will not be available due to system maintenance
or mechanical breakdown.
In the former instance, this will normally take place at night or on weekends
and users will be warned if possible.
It is very important that when a message to log off\*F is received,
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such a message might be: 'System down for 5 minutes. Please logoff now!'.
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you comply as quickly as possible.
This is for your sake and the sake of your files.
.H 2 "Where Are The Terminals?"
The terminals at the AGSM are located in
several rooms.
The main terminal laboratory is
room 422,
which contains all of the student
terminals.
These are the terminals which
can be used outside normal hours.
There are also three terminals
in room 436,
which are for the use of
AGSM staff.
Because this room contains the QUME, it is commonly known as the 'QUME' room.
There are also two terminals
for use of AGSM staff at Botany street.
.H 2 "The Line Printer"
The line printer is located in room 410.
As well as having a fast upper case only
line printer,
there is also a smaller printer,
called a 'DECprinter'.
This small printer is not quite as
quick as its larger brother,
but it prints both upper and lower case.
To access this smaller printer
you type
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% lpr -1 [your files...]~~~~~( note it is the digit one, not a small l)
.DE
which is the same as for the larger
printer,
except that '-1' is omitted.
You will obtain a listing essentially
the same as the larger printer,
except that lower case letters will be printed in lower case.
The use of the printers will be explained in greater
detail in coming sections.
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If either of these printers
is out of paper,
please consult the system staff\*F.
.FS
the system staff (as of February 1979) are
Ian Johnstone
(Rm 437, extension 3752)
and
Andrew Hume
(Rm 435, extension 3814).
Any personal "mail" (see section 5.1) can be addressed to 'ianj' and 'andrew'
respectively.
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.H 2 "What To Do If Something Goes Wrong"
By 'wrong', we mean 'not as expected'.
Therefore, treat unknown messages as errors and act accordingly.
Ask someone who does know!
Most queries can be answered by almost any other user, so don't be afraid to
ask.
If no one can help, ask the system staff.
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Again I must stress the importance of
contacting someone if anything out of the
ordinary happens.
This applies particularly if you find a hardware\*F
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e.g. a terminal that won't communicate or a line printer which is out of paper.
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or a software\*F problem.
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e.g. a program that doesn't work (but make sure you know what it's doing).
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If you don't tell the system staff, they may never know!
If you can't find them,
mail "root" with the message or even pin notices to their doors.
.H 2 "Computer Users Ethics"
In view of recent reports
of wilful misuse of the
University's computing facilities,
the following Code of Ethics for users is
brought to the attention of all users.
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The computer is provided for the use of registered
staff and students.
The facilities of the system are available
for use by staff for appropriate teaching,
research and administrative purpose,
and by students for assignments or research
in approved courses for which they are registered
users.
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The resources of the system are finite and in great
demand and therefore are not to be wasted or consumed
by inappropriate or
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irresponsible computing.
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Users should therefore avoid:
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Producing unnecessarily long and/or badly
formatted computer output.
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Repeatedly executing programs which have failed without
having made proper efforts to locate the error,
or without having included debuging printout
statements.
Computer errors are very rare.
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Running long programs using inefficent
algorithms.
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Users should not attempt to gain
an unreasonable share of resources.
Activities not allowed include
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Excessive occupancy of computer terminals.
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Using false names or other subterfuges to gain
an excessive allotment of time on terminals.
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Users must adopt a reasonable attitude to operation
of the equipment.
Users should:
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Report promptly any machine failure
and must not abuse equipment nor attempt
to correct faults,
for example,
by replacing blown fuses.
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Keep terminal areas clean and tidy,
especially disposing of paper after
terminal sessions.
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Never eat, drink or smoke
near computer equipment.
This is because of possible damage to the equipment.
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Respect other user's output by not remaining
or interfering with printout except to separate
outputs and shelve output.
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Users will be liable to disciplinary action for
serious misuse of the resources
or causing wilful damage to network operations.
Such activities include:
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Attempting to crash the system.
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Attempting to circumvent the security
and privacy features of the system.
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Unauthorised use of other people's accounts
or files.
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