LabVIEW incorporates shortcut key combinations that are equivalent to some of the pull-down menu selections. The shortcuts are displayed next to the items in the menu. The key combinations that are most helpful while you are programming with LabVIEW are listed in Table 1.2. There are also some shortcuts that are not found in the menus. For example, you can use the Tab key to move through the Tools palette. This is a quick way to change to the tool you need. The spacebar lets you toggle between the Positioning tool and the Operating tool. The normal key combinations used in Windows and Macintosh for save, cut, copy, and paste are also valid.

1.6 FRONT PANEL CONTROLS

Numerous front panel controls are available in LabVIEW for developing your applications. The Controls palette (shown in Figure 1.9) appears when you make the appropriate selection in the Windows menu. The controls are grouped into categories in a tree. Categories now include things like the modern control palette,the classic control palette, and specific use selections such as express VIs, and application control references. The subpalettes have a lock in the top left corner to keep the window visible while you are working with the controls. When creating a VI, controls can be simply dragged from the palettes and dropped on the front panel. A terminal, representing the control on the block diagram, then appears for use according to the program. Controls are basically variables that can be manipulated in the code. The following subsections will briefly describe the various control palettes. The Connectivity palette includes .NET and Active X references and will be described in Chapter 8

 FIGURE 1.9

1.6.1 USER CONTROL SETS

The first three branches in the control tree are modern, system, and classic. These three sections contain all the controls that an application user would interact with such as data entry controls and file path controls. The controls will behave and present data according to the operating system running the application. There is no need for us as programmers to worry about the epic battle between Windows and Linux and the use of a forward or back slash for directory listings.

The system palette contains fewer controls than the classic and modern palettes;in fact, all system controls are strictly user interface controls. Classic and modern palettes contain additional controls that have appeared in previous versions of LabVIEW. The following sections describe the control palettes as they appear in the classic and modern tree sections. The primary difference between them is appearance on the display. A classic numerical control will store data internally as a modern palette control.

1.6.1.1 Numeric

Internally, LabVIEW supports a number of numeric data types. Main types are floating point, integer, and complex numbers. Each type supports three levels of precision. Floating-point numbers are available as single, double, and extended precision. LabVIEW defines the number of digits in the mantissa for single and double precision numbers. Extended precision numbers are defined by the hardware platform LabVIEW is executing on. Integers are available as byte, word, long word, and quad word precision. Bytes are 8-bit numbers, words are 16-bit numbers, long words are 32-bit numbers, and quad words are 64-bit numbers. Integers may be used as signed or unsigned quantities. LabVIEW supports 64-bit integers on all platforms; 32-bit machines will use code to emulate 64-bit integers. The controls in the Numeric palettes for the classic and modern sets are displayed in Figure 1.10. A full set of controls for allowing a user to enter and view data exists. Simple text representations exist for displaying data in addition to a variety of styled, graphical controls for presentations. User interfaces benefit from a set of controls that are relevant to the application. For example, an application supporting automation of operations at a brewery would benefit from using the tank controls to show the fill level of a primary fermenter. Choice of controls should be used with prudence. An application that contains a dizzying array of colors, styles, sizes quickly becomes an eyesore for a user. Use controls to design an appearance that a user will relate to. Palette selection is not mutually exclusive — for example, using a tank in the classic set does not eliminate LabVIEW简介英文文献和中文翻译(6):http://www.751com.cn/fanyi/lunwen_51997.html