The Hacker's Encyclopedia 1998

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PRODIGY(R) interactive personal service INTRODUCTION You may have recently read about data from other files appearing inside the STAGE. This is a harmless side effect of DOS file operations and the process by which the PRODIGY STAGE is created. On the following screens you'll find a discussion of your STAGE.DAT file. If you're interested in the details, please read on. I think you'll be more comfortable once you've read the facts. Harold Goldes (CBXH97A) Technical Editor, PRODIGY Star READING MY HARD DISK? The occurrence of "non-PRODIGY" data within the disk space used by the STAGE has prompted some to speculate that PRODIGY can gain access to that information or other information on a member's hard disk. Here are the facts: The PRODIGY software does not examine a member's hard disk as a whole. It does not read files created by other software. It does not read data other than its own. It does not upload files to do this. The PRODIGY software confines its file operations to a limited and well defined section of your disk: The PRODIGY directory. ABOUT THE STAGE When you install the PRODIGY software on your computer we create a unique file on your floppy or hard disk: STAGE.DAT. The STAGE (or STAGE.DAT as it appears in your directory or folder) is a "container". What does it hold? The STAGE contains frequently used information and instructions that make up PRODIGY applications ("applications" refers to the individual activities available to you on the service; FIND and the Movie Guide, are examples). LOCAL STORAGE Placing portions of applications on the STAGE (and not in other more remote parts of our network) puts them close to you. Without a storage structure like the STAGE, key components of an application would be sent to your computer whenever you visited the application. This adds transmission time. Placing them on your computer saves time. When you install the DOS version of the PRODIGY software, you have the choice of creating the STAGE in a range of sizes from about 160Kb to 950Kb. For Macintosh users there is one size: 200,064 bytes. STAGE SIZES If a member installs to a floppy disk(s), the STAGE may vary in size. These intermediate sizes depend on several factors including the capacity of the disk and the version of DOS. Once it's been created, the STAGE never changes its size. But the date and time stamp on the STAGE does change and is updated at the end of every PRODIGY session. This reflects the fact that during your session we read PRODIGY content from it and write updated PRODIGY content to it. To improve performance during your session, certain frequently used parts of the service are always "staged". A larger STAGE, should you choose one, permits a growing inventory of applications to reside on your computer. Because our software adapts itself to you, some of the content you use regularly can become staged. BENEFITS Whenever and wherever you logon to the Prodigy service, we check to see if you've got the latest versions of a variety of programs and data that reside in the STAGE. If not we send you what you need. You don't have to ask for new disks. And you don't have to reinstall. RAMDISKS Some members use RAMdisks to improve performance. A RAMdisk is a "disk drive" made from memory (RAM) not from mechanical parts. It's faster than its physical counterpart but can more easily lose data. For that reason we don't recommend using a RAMdisk. However here's something to keep in mind if you're going to do it anyway. A RAMdisk is volatile. If you turn your machine off, the information stored on the RAMdisk evaporates. As you may be receiving an update each time you sign on, be sure to save the updates. To do this, copy the file named STAGE.DAT back to your PRODIGY directory before you hit that switch. NO UPDATE NEEDED Members often ask about the need to update the PRODIGY software on their PRODIGY installation disks. There is no need to update the original installation disks. Use those disks (or backup copies) to install the software on any computer you use to sign on to the PRODIGY Service. Then, when you sign on for the first time, the service will automatically update the PRODIGY software. DUAL COMPUTERS Suppose you have two computers and use them both to access the service. Let's say you use one more frequently than the other. Each of your computers will get updates, if needed, when you use them. The machine used most frequently will be updated steadily (almost imperceptibly) by increments. When you use the other machine, you might notice a delay during logon because it's receiving a greater amount of updated information all at once. LIMITS There's a practical limit to the kinds of changes we can make automatically to an existing version of the software. If you've ever tried adding air conditioning to a car you bought without it, you'll understand this; sometimes it's best to start over with the really useful options built in. So over time when we make extensive improvements to the PRODIGY software, we may send you a new set of disks. NON-PRODIGY DATA From time to time members using the DOS version of the PRODIGY software see information from "other" (non-PRODIGY) applications in the disk space used by STAGE.DAT. Data from non-PRODIGY files is never actually part of STAGE.DAT. More importantly it is never accessed or uploaded by the PRODIGY software. There are two ways in which extraneous data can appear in the STAGE. In the first case, the data was originally located in areas of the hard disk once used by other software. At one point in the past, this data was erased. DOS FILE DELETION When you erase a file, PC-DOS or MS-DOS (the operating system for personal computers) does not remove the file's contents from your disk. Instead it only marks the space used by the file as now "available for use". In doing this, it gives other software permission to reuse that space. Until that space is used by its new owner, the old data remains. This is why certain "unerase" software packages can recover accidentally deleted files. When you install the PRODIGY software, it asks DOS to supply disk space for the STAGE.DAT file. Depending on the size of the STAGE you choose, this is usually a request for anywhere between 160Kb to 1 Mb. DOS PROVIDES FILE SPACE DOS then checks its inventory of available disk sectors, finds the space and reserves it for its new owner: STAGE.DAT. But DOS leaves any old data in that space intact. Please keep in mind that DOS simply supplies the sectors we request (as long as they are available) and does not touch their original contents. Next, our install program starts filling the space with blocks of PRODIGY information. The PRODIGY install program does not erase any old data because to do so would appreciably lengthen the install process. As a result, old "erased" data may appear in unused space following the blocks (where it's more noticeable) as well as in smaller areas that occur within the blocks (for more on this see "HOW WE USE SPACE" below). ROOM TO SPARE If you chose a large STAGE (anything from 250Kb to 950Kb), chances are that at first, a portion of it will be unused. It is likely that some of the space within that unused portion was used by other software at one time. If so what you'll see if you examine that area will be "leftovers". Over time, the PRODIGY software will write blocks of information to the STAGE replacing whatever is there. Please keep in mind that the PRODIGY software can only recognize the blocks of information that it puts into STAGE.DAT itself. It does not read, collect, process or transmit "non-PRODIGY data". All disk space containing such data is treated as empty. STANDARD TECHNIQUES Like most major software, to ensure compatibility and reliability when creating, reading and writing files, the PRODIGY software employs standard "services" provided by your computer's operating system. By viewing the STAGE with certain software tools, members have observed information from non-PRODIGY applications. However the PRODIGY software can neither see this information nor use it. To the PRODIGY software this space is considered "empty" and available for storing PRODIGY data. Over time, as you use the service, this "empty" space is covered by PRODIGY content. HOW WE USE SPACE When we store data in the STAGE, we do it via DOS in blocks of a specific size. Let's say that size is 100 bytes. If we store a 120 byte "object" then we use two blocks (or 200 bytes of storage). What we store takes up all of the first block but only 20 bytes of the second block. What happens to the remaining 80 bytes of the second block? Whatever was there originally remains. If that block was built on a previously used sector, 80 bytes of "old" data will be seen. DATA FROM A DIFFERENT DISK There's a second way in which extraneous data may appear within the disk space used by the STAGE. When the STAGE is being created, certain "control" areas may incorporate information that was in your computer's memory (RAM). These areas are used by the STAGE itself to keep track of its own contents. This extraneous data may include non-erased data or data from another disk. You may observe the names of directories, your PATH, or information from the software you were using just before you installed the PRODIGY software. To minimize the occurrence of this data within the STAGE, just turn your PC off, wait 15 seconds then turn it on again before installing the PRODIGY software. FOREVER SEPARATE In short, extraneous information can appear in the disk space used by the STAGE and yet not actually be part of it. The appearance of this "non-PRODIGY data" is a side effect of DOS file operations or the process by which the STAGE is created. But, like a bottle containing oil and water, this disk space STAGE can contain both PRODIGY and non-PRODIGY data which are different and remain separate. REMOVING EXTRANEOUS DATA? The PRODIGY software does not read information created by other software. And it does not read data other than its own. Nevertheless some members have tried to delete non-PRODIGY data from the STAGE by using file editors. Modifying the contents of the STAGE file will do more harm than good. To maintain the integrity of the STAGE, we use special techniques that detect alteration of its contents. "NO USER SERVICEABLE PARTS" Changing the contents of the STAGE with a software tool (like an editor) will render the STAGE unusable. You'll have to reinstall the PRODIGY software. For those members who are concerned by even the appearance of extraneous data within the STAGE, we are preparing a utility to eliminate non-PRODIGY data from the STAGE. CONCLUSION No extraneous information appearing within the disk space used by STAGE.DAT is known to or used by PRODIGY. The only information used by the PRODIGY software is what is needed for the installation and operation of the software.