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.




	TIP: 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.

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.




	TIP: You may turn off your terminal at the end of the day, because doing so does not affect the computer's operation.

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.




	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 9X8LX, 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.

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.




	TIP: 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.

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.




	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.

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.




	TIP: Disk drives, tape drives, and terminals are peripherals, just as printers are.

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.