LabVIEW简介英文文献和中文翻译(3)

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FIGURE 1.4

1.1.4 LABVIEW FILE EXTENSIONS

LabVIEW programs utilize the .vi extension. However, multiple VIs can be saved into library format with the .llb extension. Libraries are useful for grouping related VIs for ﬁle management. When loading a particular VI that makes calls to other VIs, the system is able to ﬁnd them quickly. Using a library has beneﬁts over simply using a directory to group VIs. It saves disk space by compressing VIs, and facilitates the movement of VIs between directories or computers. When saving single VIs, remember to add the .vi extension. If you need to create a library for a VI and its subVIs, you will need to create a source distribution using the LabVIEW Project.If you want to create a new library starting with one VI, you can use Save or Save As. Then select New VI Library from the dialog box. The File Manager can then be used to add or remove VIs from a library.

1.2 LABVIEW PROJECTS

Among other features in LabVIEW 8, the one you should be interacting with daily is the project view. LabVIEW’s new project view provides a convenient interface to access everything in a LabVIEW project. Historically, locating all the Vis in an application has required the use of the hierarchy window, but that does not locate some things like LabVIEW libraries and conﬁguration of the application builder. The project explorer provides a tree-driven list of all of these. The set of VI sources and libraries are shown in the ﬁrst major breakdown: the Source tree. Information related to compilation and installation of an application are kept in the second branch of the tree: Build Speciﬁcations. Information relating to the target machine environment you are building an application to is located in the last branch: System Deﬁnition. Applications that use the same operating system as the development platform will not ﬁnd the System Deﬁnition folder to be of value. If a compile target is something like a Palm Pilot, then this folder is where deﬁnitions speciﬁc to a Palm based target would be conﬁgured. The project window is shown in Figure 1.5.

FIGURE 1.5

Among other things worth noting on the project explorer window is the toolbar, which contains buttons to create, save, and save all VIs in the application; compile; the standard cut, copy, and paste buttons; buttons to support compilation of VIs; and buttons to support source code control tools. All of these features will be elaborated on in Chapters 2 and 4.

In general, most work will be done in the Sources branch which provides a listing of all VIs and variables in the project. The Dependencies section is for VIs,DLLs, and project libraries that are called statically by a VI.

1.3 HELP

For beginning users of LabVIEW, there are various sources for assistance to aid in learning the language. Because this book is not a comprehensive guide for beginners, this section was prepared to reveal some of these sources. LabVIEW’s builtin help tools will be shown ﬁrst, followed by outside references and Websites. LabVIEW’s online reference is an excellent source of information on the operation of various LabVIEW elements, error code deﬁnitions, and programming examples.Few languages can boast of having an online help system that is put together as well as LabVIEW’s.

1.3.1 BUILT-IN HELP

The ﬁrst tool that is available to the user is the Simple Help. This is enabled by selecting this item from the Help pull-down menu. When selected, it activates a balloon type of help. If the cursor is placed over the particular button, for example, a small box pops up with its description. This description contains information such as the inputs and outputs the VI accepts in addition to a short text description of what the VI does. Balloon help is available for all wire diagram elements, including primitive elements, National Instruments-written VIs, and user-developed VIs. This tool is beneﬁcial when ﬁrst working with LabVIEW. It is also helpful when running VIs in single-stepping mode to ﬁnd out what each of the step buttons will execute.