Within the PowerHome environment, you have access to two types of variables.  The first are global variables which can be unlimited in number and are defined by the user and the second are system variables which are finite, some of which can be indirectly created by the user.  Global variables are created from within the global variable maintenance section of the PowerHome Explorer.  Once created, their values can be changed over and over again from within macros and formulas.  A global variable will retain its state or value until changed.  Even if PowerHome is shut down, restarted, or the computer should physically lose power, a global variable will retain its last value.  Global variables are referenced from within formulas by their ID name (UPPER CASE A MUST) surrounded by curly braces or through an appropriate formula function.  A global variable defined within the global variable maintenance section with an ID of TEST can be referenced via variable substitution as {TEST}.  A system variable is similar to a global variable in that it stores information, but system variables are not defined by the user.  System variables also are reinitialized everytime PowerHome is started.  They DO NOT retain their state.  Some system variables cannot have their values directly changed either.  System variables are referenced by their name surrounded by square brackets (UPPER CASE A MUST) or through an appropriate formula function.  An example of a system variable via variable substitution is the sunset system variable [SUNSET].  Variable substitution occurs when you have text with references to system and / or global variables.  The way this substitution process takes place is with a repetitive search and replace loop.  When a formula is processed for variable substitution, global and system variables are searched for from the start of the formula.  If a global variable is found first, its value is looked up in the database and substituted for the global variable reference.  If a system variable is found first, its value is referenced from memory and substituted for the system variable reference.  This process is repeated indefinitely until no system or global variables exist to be replaced or until the max variable substitution limit is reached.  This limit is set in the PowerHome Setup section under Script.  Note that it is possible for global and system variables to contain references to other global and system variables.  When a global or system variable is substituted, if the value is a number, you should be careful to place a space before and after the global or system variable if any math is to be performed.  This is to solve the problems one will encounter when trying to perform math on global or system variables and not placing a space between the operators and the global or system variables.

NOTE:  When referencing global variables and system variables with variable substitution from within formulas, remember to CAPTITALIZE the ID name.  If this is not done, it will not be recognized as a variable and no substitution will be performed.  Certain Send Keys sequences can appear as a global variable and will be looked up in the global variable table.  If not found, they will then be treated as a Send Keys text and not be substituted.  For this reason you should not name any global variables F1 through F12 because {F1} through {F12} is a valid Send Keys string.  A special case of curly braces is included in the global variable substitution function.  An open and close curly brace with nothing between them, ie. {}, will be removed during the substitution and not left in the result as would be the case with any other use of curly braces that is not a global variable.  This special situation is useful when dealing with certain issues of ODBC databases which prevent one from storing certain combinations of characters in the first position.  An example of this is trying to store {DSS POWER FLAG} in a formula.  The {D is assumed to be an ODBC control character.  You can eliminate this problem by placing the open and close curly braces in front of the global variable like this: {}{DSS POWER FLAG}.  Since the open and close curly braces will be removed during substitution, the net effect is the same as if they never existed.

PowerHome has a number of formula functions which allow you to access the contents of global and system variables without using variable substitution.  These functions will return the variables data as the specific data type you request within the formula.  Using these functions is slightly more efficient than variable substitution as the functions access the variables contents at evaluation time instead of being searched and replaced prior to formula evaluation.  You can find details on these functions in the online help or the function appendix under ph_getglobal, ph_getsystem, and ph_getvar.

You can also disable variable substitution by editing the pwrhome.ini file and setting the VARSUBSTITUTION parameter under the [Script] section to NO. To enable variable substitution, set this parqameter to YES. You can also enable and disable variable substitution via code with the ph_varsub function. You can retrieve the status of the variable substitution parameter with the ph_getvarsub function. Disabling variable substitution means you'll have to use the ph_getvar, ph_getglobal, and ph_getsystem functions exclusively in order to reference variables from within a formula but has the benefit of allowing PowerHome to run as fast as possible.