HP 3000 Manuals HP 3000 Manuals
Destinations for Information
Where information goes depends in part on where you want it to go and
your reasons for sending it there. In part, where information goes is
determined by the command or program that you are using and by the
computer itself.
Computer memory
Computers have not one but several forms of memory. Which kind of memory
is devoted to your work is determined by the stage at which you find
yourself.
Random access memory (RAM).
If you are using a text editor, such as EDIT/3000, all--or certainly
some--of your text will reside in the computer's active memory while you
are working on the text. Active memory is called random access memory.
At the same time, a certain portion of the computer's active memory is
occupied by the text editor program itself.
When you start an editor program (by executing EDITORReturn, for
example), the computer loads the program into random access memory and
begins following the instructions that it finds in the EDIT/3000 program.
If you then specify an existing text to edit (TEXT REPORT1Return--meaning
"call up the file named REPORT1"), the program calls upon the computer to
load the file called REPORT1 into random access memory as well. How much
of your text is actually loaded into random access memory depends upon
how much memory is available at the time. If you begin by creating new
text, that text is placed into random access memory as you type.
Still other parts of random access memory are occupied by the computer's
operating system and by the programs and information that other users are
working on at the same time. In the background, the computer itself may
load, run, and unload other programs in order to carry out its own tasks
or the tasks that you and other users assign to it.
The amount of memory taken up by "background" programs and processes is
called overhead. In a very real sense, overhead is an "expense" incurred
by any program that you might use.
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|Because random access memory in any computer is finite, specialized |
|programs exist to "fine tune" the management of this vital commodity. |
|In fact, one or more of these memory management programs may be |
|running in the background while you are working on something of your |
|own. |
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The active portion of the computer's memory exists only in electronic
form and exists only while the computer is active (receiving electrical
current and operating normally).
RAM holds those programs that you or the computer are running, as well as
information (data) that the programs are working on--the text of your
letter, for example.
Random access means that, with certain exceptions, material in RAM is
available for your use at will. If you decide to insert a new line or a
new paragraph in the text that you are writing, the editing program
permits you to do that. By adding a new line or a new paragraph, you are
inserting data into the computer's RAM memory. You may examine any
portion of your text without having to start at the beginning and work
your way down to the portion that you wish to see.
Disconnect or seriously interrupt the current, and everything in random
access memory disappears. This is one reason that you will almost never
turn off your MPE/iX computer. Equally important, turning the computer
back on is not simply a matter of turning the switch from OFF to ON. All
of the background programs and processes that the computer relies upon
for its operation must be reloaded and synchronized. That takes time.
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|You may turn off your terminal at the end of the day, because doing so|
|does not affect the computer's operation. |
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When you log on, when you run programs, the computer devotes a portion of
its random access memory to your session and to the commands and programs
that you are using. It devotes some of its random access memory to every
user who is logged on to the computer. It reserves some memory for its
own purposes, too. When you log off, the computer reclaims the portion
of memory that was devoted to your session and your work and, if needed,
reassigns that portion of memory to another session or program.
Random access memory is large, but it has limits. As more and more users
log on, as they run more programs, or more complex programs, the computer
can devote less of its time and memory to each user. At some point, the
computer becomes so busy doing "a little of this and little of that" that
users begin to notice that their work is slowing down. At this point,
the system operator may have to step in and limit the number of jobs and
sessions that are actively running, simply to allow the computer to
reclaim some memory and to spend more time with the remaining sessions
and jobs.
Your MPE/iX computer is well-designed to deal as efficiently as possible
with a large volume of work. Still, you should be aware that on
exceptionally busy days, your work might slow down, or your operator
might impose limits. The operator might suspend some jobs--and resume
them later. Or you might try to log on and find this message on your
terminal:
CAN'T INITIATE NEW SESSIONS NOW
Read only memory (ROM).
Read only memory (ROM) is another form of computer memory. Like RAM, it
is electronic. Unlike RAM, it is stored permanently inside the computer.
ROM is inaccessible. You can neither add to nor take away from the data
that resides in ROM. It holds information that is vital to the computer's
second-by-second operation.
Disk--saving information
Information that is vital deserves to be saved. When you have finished
working on your information, you must transfer that information from RAM
to a computer disk memory.
Almost every program has a command or a technique that permits you to
save your information to disk. The EDIT/3000 program does this through
its KEEP command: KEEP REPORT1Return instructs the program (and the
computer) to move the information from RAM into a disk file called
REPORT1.
If you leave a program without this vital, saving step, there is a chance
that you will lose whatever you have added to RAM--the rest of that
letter that you decided to finish writing today. Sophisticated programs
will alert you and ask whether you really intend to leave the program
without saving your latest efforts.
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| |
|Worth Remembering |
| |
|In the event of a loss of power or a catastrophic failure, information|
|in RAM can be lost. Sophisticated computers, such as the HP 3000 |
|Series 9X7LX, will attempt to save information from RAM to disk in the|
|event of a catastrophe. EDIT/3000 saves information in temporary |
|files that have names such as K910805. The numbers form a code |
|indicating by year, week of the year, and day of the week, when the |
|file was saved (1991, week 08, day 05). |
| |
|You should pause in your work from time to time and issue a save |
|command through the program that you are using to put your information|
|into a disk file. |
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Tape--protecting information
In comparison with RAM, disk memory seems almost permanent. Once
recorded onto a disk, information is generally secure from loss.
Secure as it seems, disk memory is not truly permanent, nor should it be
regarded as permanent--certainly not for information that you cannot
easily replace or recreate.
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|At some time, almost every person succeeds in accidentally erasing |
|from the disk at least one file. Almost without fail, it is the one |
|file that you need right now. |
| |
|If a file is important, store it safely on tape. |
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Almost every computer system provides some means for saving vital
information in a safe, protected environment. Transferring, or copying,
information from a disk to a magnetic or digital tape is a common and
economical means. The process may be called backing up or archiving.
The term associated with MPE/iX computers is storing, from the command to
perform this operation, STORE. Its complementary process, returning
information from a tape to a disk, is called restoring (from the RESTORE
command).
Still another reason for storing information to tape is economy. Disk
memory, though large, is finite. Unless you can afford to purchase new
disks and disk drives as you need them, you will eventually fill your
existing disk(s) with information.
The more economical solution is to store files onto tape when they are no
longer of immediate or near-term value. Then erase from the disk those
files that are safely stored. The disk space taken by those files
becomes free again. If that stored information is needed again, you may
restore it to your system--provided you have kept enough free space on
your disk(s) to accommodate those restored files.
Backing up files: full or partial.
A full backup copies all user files on the system regardless of when they
were created or last changed.
A partial backup copies only those files that have been created or
changed since the last full backup.
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| |
|Worth Doing |
| |
|Establish and adhere to a schedule for backing up the files on your |
|computer. |
| |
|Your backup schedule should include both types of backup. A typical |
|backup schedule allows for one full backup one day a week, and a |
|partial backup on each remaining work day. |
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When the person managing your system warns you that a backup is
impending, heed any instructions to save the work that you are doing and,
if requested, log off. During a backup, you will not be permitted to
continue working or to log on and start new work.
The process of backing up depends upon having files that do not change
during the backup. When the backup concludes, you will be allowed to log
on again and resume your work.
Printers
For most of us, there is a value in having information on paper, if only
to send that piece of paper to someone else. Many of us are simply more
comfortable seeing something on paper, as well as on the computer screen.
For that reason, a computer without a printer would lose much of its
value to us.
Collectively, printers are considered one of many classes of devices that
may be connected to a computer. Loosely defined, devices are those
pieces of equipment that are connected to a computer that are not
essential to the internal operation of the computer itself. Any device
that is not inherently part of the computer itself is a peripheral
device.
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|Disk drives, tape drives, and terminals are peripherals, just as |
|printers are. |
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You may attach one or many printers to your computer. Which kind of
printer you choose depends upon the nature of your work and the degree to
which you need (or want) to be able to create documents that approach the
quality of printing obtained from a professional printer.
For many purposes, only rough or intermediate quality print is
sufficient. For such purposes, line printers are likely to be adequate.
Line printers take their name from their technique of printing one line
at a time. Page printers print an entire page in one operation. For
most purposes, laser printers, which are also page printers, provide the
highest quality print definition.