A macro acquires a value in one of two ways: implicitly when the software encounters a call to a previously unknown global macro, or when a local macro is unassigned in a macro call program explicitly in a LET or INPUT command (global or local macros), or in a call to a procedure (local macros…
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A macro can appear anywhere and can be repeated any number of times in an application program. Each time the software encounters a call to the macro, it substitutes the current character string value of the macro. Substitution takes place one command at a time, before each command is executed. To view these substitutions as…
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When the result of a functional expression is a numeric value, the result contains as many decimal places as are found in the arguments of the function. If the function has several arguments with varying numbers of decimal places, the result takes on the number of decimal places found in the argument with the most…
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Expressions can be combined in special ways to produce concise program statements that nevertheless have tremendous power and flexibility. The special expression formats are WHERE expression format assignment expression format grouped expression format case expression format How To Use the WHERE Expression Format A WHERE subcommand can be appended to a value expression to control…
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The software maintains a series of system variables that represent either fixed values ($ZimOS) or values that fluctuate dynamically with the current status of the software ($InTransaction) or of application objects (ThisWindow.WindowTag). System variables resemble global variables in nature. The software automatically sets or resets the values of system variables to reflect the status of…
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Although every application has its own unique requirements, the individual components of applications are often very similar. For example, menus, pop-up windows, and data entry forms and displays are common components of most applications. Pop-up windows, for instance, can vary in size, location and contents, but the commands to present them to the application user…
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An object that has not been assigned a value, or whose value is unknown, is considered to be $Null. For example, at the start of an application session, global variables do not have an assigned value, so each is considered $Null. If the name of an object with an unassigned or unknown value is used…
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Operator Rule of Precedence Conditional Operators are evaluated first NOT NOT is evaluated first. AND AND is evaluated next. OR, XOR OR and XOR are evaluated last. Note: Operators of equal precedence are evaluated from left to right in the expression.Parentheses can be used to explicitly determine the order of evaluation, overriding the order described…
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Boolean expressions use Boolean operators to compare operands (typically, conditional expressions). When evaluated, Boolean expressions yield a logical result (true or false), depending on the nature of the Boolean operator and the values of the conditional expressions. The standard rules of precedence for Boolean evaluation are used. The software ceases to evaluate a Boolean expression…
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A null string is a character string of zero length. Unlike the $Null property that indicates that the value is unknown or unassigned, the null string is a known value. For example, if you have two variables, x and y, both of which are null strings, then the expression x = ” and y ‘abc’…
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