open-system approach is the Labtech Notebook (LTN) software package de signed by a team at Laboratory Tech nologies Corporation. This software package is primarily for real-time ana log data acquisition and control. It also does some data analysis (FFTs and nonlinear curve fitting). The soft ware was designed to provide an easily learned package for use on a personal computer. The level and type of pro tection in each layer can be adjusted independently for the application at hand. Each layer in L T N (Figure 2) com municates with the other layers through disk data files. These data files have a number of formats, one of which is human-readable ASCII for mat. ASCII files have the great advan tage that they can be created and modified with conventional text pro cessors and can be read and written easily by all programming languages and most applications packages. The formats of the other communicating data files are also rigidly specified. Each of the layers can receive its data files from either standard LTN mod ules or customized modules that the users might create. The various layers and their protection levels are de scribed in the following paragraphs. L T N programming language is an
CORRECT BASELINE
interactive, incrementally compiled language (similar to FORTH in struc ture and to Pascal in syntax). At this level users can write programs at will, and there is complete access to their completely unprotected source code files. The nucleus of the language is protected by a key lock system as de scribed above. LTN menu code provides menus that are protected from modification by naive end users but that can be modified extensively by expert users, vertical application developers, and instrument manufacturers. The menu code creates and manipulates the method library, which interfaces to the next two layers. The LTN data acquisition and con trol code responds to setup informa tion in the method library and gathers data in real time from laboratory in struments and sensors. It also allows the computer to be used for any other program while the data are being gathered. Because this code is ex tremely critical and advanced (the in tegrity of the user's data depends on it), and also because it is proprietary, it is completely protected from user modification and supplied entirely in machine-readable form. LTN data analysis codes operate on data files created from real-time ex
periments, on data that have been brought in from other systems or even data typed in at the keyboard. Each of the data analysis codes is a separate layer and has a different level of pro tection. User-supplied analysis codes may consist of off-the-shelf software pack ages like Bolt, Beranek and Newman's RS/1 or Lotus Development's 1-2-3 (protected). Alternatively, they may be analysis programs developed by us ers in their favorite languages (pro tected or not, depending on the user's needs). LTN 1-2-3 worksheets are supplied in unprotected source code as part of LTN. These perform spreadsheet data analysis and graphic display and are provided in source form so that end users can modify them at will to evolve their own custom data workup spreadsheets and graphs. Once these worksheets have been developed, 1-2-3 allows them to be protected on a cell-by-cell basis. In summary, protection of software is an interesting area with many dif ferent and seemingly conflicting re quirements. Software technology has evolved, however, to accommodate all these varied requirements without compromising the effectiveness of the systems.
GC/LC SHIFT!
AZ-1436 STAND-ALONE DETECTOR
AUTO-ZERO Zero positive or negative drift from any GC or LC detector. Zero automatically (i.e. data system flag) or manually to true zero ±3μν. Autozero between runs, peaks, peak groups. •
No effect on detector or chromatography, Improves signal transfer.
improved Results lor Atomic Absorption B&J Brand™ High Purity Methyl Isoamyl Ketone assures better performance results for atomic absorption. Extremely low background metal content and low residue are the reasons. Not to mention the consistent high purity, which you can always expect from American Burdick & Jackson. For complete information on B&J Brand Methyl Isoamyl Ketone and other solvents that make your lab work easier and more accurate contact American Burdick & Jackson, 1953 South Harvey Street, Muskegon, Ml USA 49442. Phone: 616 726 3171.
SYSTEC, INC. 3ΗΊ6 Cliundlei Dnvt Minnuj"ulib MN 55421
American Burdick & Jackson subsidiary of American Hospital Supply Corporation
(612) 788-9701 ©1985 Amertcan Hospital Supply Cor(Kiiat»n
CIRCLE 189 ON READER SERVICE CARD
818 A · ANALYTICAL CHEMISTRY, VOL. 57, NO. 7, JUNE 1985
CIRCLE 8 ON READER SERVICE CARD
