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The "Expressions" functionality, or more specifically the expression processing engine, is the primary mechanism which allows extensive customization of forms, queries, reports, color schemes, and other elements of Campground Master. This is essentially a programming language with many built-in functions to access data, manipulate information, and generally get at any particular information you need. Since expressions are used in all of the advanced customization functions, you will need to get familiar with them in order to do your own customization.
In simple terms, an expression can be thought of as a calculation, or mathematical expression. If you're familiar with formulas in Microsoft Excel, or expressions used in Microsoft Access or dBase queries, then you'll have a big head start. For Scripting, familiarity with programming languages like Basic or C will help.
Expressions can be very simple or very long and complex, but every expression ultimately evaluates into a single value. This value can be a number, a string of text, a date, a boolean (true/false) value, or a data record pointer. The type of expression needed depends on the situation. For instance, boolean expressions are used in many places for filtering data or where conditional logic is needed like color schemes. Numeric expressions are used where calculated numbers are needed like transaction reports, and text expressions are used where text should be displayed such as receipt forms or query columns.
Macros are single expressions that can be called by name, with optional replacement parameters. They allow re-using common expressions, or simplifying things by calling a complex expression inside another expression. If you're familiar with Macros in the C programming language, they basically work the same way.
Scripts are a list of multiple expressions for performing more complex calculations, which can be called like a function from another expression. This is similar to defining a function in C or a procedure in Visual Basic or Pascal.
Additional Topics:
Advanced Customizations Overview & other topics