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COLUMN: BUILT-IN RAM: PART 1 - THE RAM DISK
The concepts of RAM Disk, RAM Card, System RAM, Total Memory, Disk Drive, File, A Drive, C Drive, Byte, Kilobyte, and Replacing Current File are explained in this column designed for novice HP 95LX users.
By Hal GoldsteinThe Vocabulary of Computers
Computers can be frustrating even to the most sophisticated user. To a "beginner," the whole experience of trying to make practical use of all the built-in capabilities of the HP 95LX can be overwhelming.
In this regular column we'll review fundamental concepts and procedures of which all HP 95LX users should be aware. These ideas will form the basis for our work on the HP 95LX and to a large extent, our work on other computers.
Learning how to use a computer means learning a new way of thinking. That way of thinking gets expressed in what we can call here "computerese," the vocabulary needed to describe computer-related concepts. The challenge of learning this new vocabulary is the interdependent nature of the concepts. That is, to understand one term, we need to understand others, which in turn often are defined by the first term. The only solution to this Catch 22 situation is repetition. Keep reading and rereading the manual and articles such as this, keep trying things out, don't be afraid to make mistakes. Eventually the whole gestalt sinks in.
Understanding the concepts presented in this regular column geared for beginning and to some extent intermediate users will enhance the practical daily use of our HP 95LX. This article will be successful if, when done, you have a clear understanding of what "saving and replacing files to the RAM disk" means. We will define terms as they are introduced.
Total Memory = RAM Disk + System RAM
Hold down the Shift key and press Filer to enter the Setup menu. At the top of the screen (in an even more important position than time, date and battery level) are three values. Total Memory equals 512 and is the sum of the values listed for RAM Disk plus System RAM. 512 here means 512K which can be thought of the capacity to "remember" 512,000 alphabetic characters.
In Computerese we use the term "bytes" instead of "characters." The "K" in 512K stands for "kilobytes," roughly 1,000 bytes per kilobyte. All HP 95LX users have 512K of RAM, of Total Memory built in. RAM is an acronym meaning memory. On the HP 95LX there are two very different types of memory, long term and short term, or in computerese RAM disk and System RAM.
The RAM disk is where we permanently store information such as the memos we write, the Lotus spreadsheets we create, our phone directory, our appointments, and our HP CALC equations. System RAM is the temporary work space where we create or modify the memo, the spreadsheet, the phone book, the appointment book, or the equations. In this article we will focus on the RAM Disk. Next time we will look at System RAM and see how the two relate.
Built-In RAM Disk
Let us say when we pressed Shift FILER, the screen showed we had a 254K RAM Disk. A 254K RAM Disk means we have room to permanently store approximately 254,000 alphanumeric characters worth of information. Maybe our phone directory takes up 25K, a Lotus spreadsheet takes 15K, and a letter we just wrote in MEMO takes 10K. If no other files were on our RAM Disk, we would have used up 50K of our 254K RAM disk to store our phone book, Lotus file, and letter.
In the last paragraph we spoke of "files." We also alluded to the built-in application PHONE, where we create our phone book; 1-2-3 where we create spreadsheets; and MEMO where we create letters.
The notion of "file" is probably the single most important concept to understand when using a computer.
To understand the concept of storing files on the RAM Disk let us look at how we might store files on a desktop computer using floppy disks. Most people have seen floppy disks - the 5 1/4" black floppy kind and the solid 3.5" colored disks.
Suppose we write a report on a desktop computer. When we finish for the day, naturally we want to save our work so we don't have to retype it all in again. On our desktop, we could save our report by giving it a name and "saving" it to the floppy disk physically located in a "disk drive." Once named and saved, our report becomes a "file" on the floppy disk. Similarly, other information such as a Lotus spreadsheet, letters and memos, or our address book, could be stored as files onto the floppy disk.
Because we can put a floppy disk in our briefcase, it is easy to conceptualize that our file is physically stored on the floppy disk. On the HP 95LX we can also store files. We store them to the built-in RAM Disk. According to what we discovered by looking at our Setup screen, we have a RAM Disk with enough room to store 254,000 (254K) worth of characters.
The built-in RAM Disk in the HP 95LX is said to reside in the "C:" drive.
The RAM Card
If we purchase a RAM Card to fit in the HP 95LX card slot, we have more room to store our files. Placing a 128K RAM Card in the card slot on the side of the HP 95LX, means we have room to store 128,000 additional alphanumeric characters (bytes) of information.
The card slot is the HP 95LX "A:" drive. Therefore, when we save files to the RAM Card in the card slot, we must save the file to the A drive. For example, to save a MEMO file to the RAM Card, we must save it as, say, A:NOTES using the "A:" prefix. If we do not give the HP 95LX a disk drive letter, the HP 95LX normally assumes we are saving to the built-in C drive.
A RAM Card operates much like a floppy disk in that after saving files to the RAM Card we can remove it from our HP 95LX and put it our briefcase for later use. (The backup battery in the RAM Card keep the files alive).
Technically, that RAM Card is also a RAM Disk. With a RAM Card, we have a built-in RAM Disk in the C drive and another RAM Disk on the RAM Card in A.
A disk, whether it be a floppy disk, a RAM disk, or a hard disk (a higher capacity disk found as part of most desktop personal computers), is a medium for permanently storing files. This is the "long term" memory we originally spoke of.
Replacing Current File
Let's look what happens when we save a file to the RAM Disk. Sup-pose we want to create a new file within MEMO. To do so, we enter MEMO and press <MENU> file new. If we are asked to "Save Changes," we enter y or n depending on whether we want to save our current work. (The meaning of "save changes" will be clearer soon.)
Now, we type some notes. For safety sake, we decide to save those notes even though we know we will be working on them again soon. We press <MENU> file save and type notes for the file name. Notice that now just below "Memo" on the top left of the screen is the name of the file we just saved, "NOTES.TXT." The NOTES.TXT file resides on the RAM Disk on the built-in C drive.
(When MEMO saves a file, it automatically adds the .TXT extension to the eight-character-or-less name you give the file. Similarly, APPT adds the .ABK extension, PHONE adds .PBK, HP CALC adds .EQN, and Lotus 1-2-3 adds .WK1.)
Let us say we add to the NOTES file and decide to save it again to be safe. This time we press <MENU> File Save. MEMO asks if we if we want to save the file as C:\_DAT\NOTES.TXT. (We'll talk about the meaning of subdirectory \_DAT in a future article). We do, so we press <ENTER>. We are now asked, "Replace current file? (Y/N)".
It is important that we understand what is happening when we are asked to replace the current file.
Currently, a file named NOTES.TXT exists on our RAM Disk. That file contains none of our recent additions. It contains only the notes we had made up to the time we originally saved the file.
Now we want to save our new work. All our additions reside in short term memory, in System RAM, not yet on the RAM Disk.
Before our HP 95LX lets us make those additions to NOTES.TXT permanent, it asks whether we want to destroy the "current" version of NOTES.TXT on the RAM Disk in order to replace it with our latest version. It asks us whether we want to "replace current file." In other words do we want to replace the current version of NOTES.TXT -- the one that exists on the RAM Disk from the first time we saved the file -- with the updated version we have been working on. We do, so we press y, "Yes."
The same sequence of keystrokes occurs when we want to update our APPT file, our PHONE book, or our HP CALC work. Similarly, when we modify our 1-2-3 work, we save the results by pressing <MENU> file save <ENTER> replace.
An unfortunate note: MEMO messages are confusing because MEMO uses the word "replace" in several ways. That is why you need to understand what is going on behind the scenes.
Suppose you added a few more sentences to NOTES. Then on impulse you decided to finish a letter you had been working on. You issue the <MENU> file open command. The message you get: "Replace file without saving? (Y/N)". The file in question is NOTES which you modified but did not save. You are being asked whether you want to bring in the letter without saving your recent work in NOTES. Answer n and you will be back in NOTES, where you can save the latest version with a <MENU> file save <ENTER> y. Answer y and you will lose your latest work in NOTES as soon as you bring in the letter.
Next time we will continue this discussion of System RAM and RAM Disk. We will examine what System RAM is in more depth and will explain why we might want to reconfigure the System RAM / RAM Disk ratio and how to do it.
In subsequent issues we will also go deeply into procedures for safeguarding and backing up our work. There is nothing more frustrating then losing the work we did on our computer. We've all lost work; however, there are definite prevention procedures. We will be examining step-by-step approaches for preventing such loss.
If you have suggestions on preventing data loss (e.g. specific
backup procedures), please write. Also, please send me feedback on whether
you found this article useful and what you would like to see in this column
in the future.
Copyright © 2010 Thaddeus Computing Inc