System Variables

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 the software and the current application. In some cases, an application program can also reset them.

A system variable name can be used as an atomic expression denoting the value currently held in the memory location associated with the variable. A system variable name can be used almost anywhere that a literal can be used.

Available System Variables

System variables are categorized into those that supply information about windows, those that supply information about menus, those that supply information about forms, and those that supply general information. Some system variables are "binary" in nature in that they evaluate only to '1' ($True) or '0' ($False), while others may be set to a variety of values.

General-use System Variables with "Permanent" Values

Given a particular version of the software, the following system variables have the same value at all times during an application session:

$ClipPath

Path to the disk directory to be used for Cut, Copy, and Paste operations that involve user interface objects in the Screen Painter.

$DBCharSet

Indicates the character set used by the application database.

$DBPath

Path to the disk directory in which the application database is stored.

$False

A "binary" false value for comparison.

$ImagePath

Path to the disk directory containing image files for use in forms.

$Null

A "null" value for comparison.

$TimeSecs

The elapsed number of seconds since 12:00am, 1 January 1970.

$True

A "binary" true value for comparison.

$WorkPath

Path to the disk directory where the application users' work fields can be found (specified in a Zim configuration file).

$ZimOS

Identifies the operating system in use.

$ZimPath

Path to the disk directory in which the Zim software is installed.

$ZimProduct

Identifies the Zim product currently being used.

$ZimVersion

Identifies the Zim version currently being used.

General-use System Variables with Values Derived from the Operating System

The software sets the values of the following system variables based on current values obtained from the operating system:

$Date

The current date.

$GroupID

The current user's operating system group identifier.

$ScreenHeight, $ScreenWidth

The size of the terminal screen in character rows/columns.

$Time

The current time.

$UserID

The current user's operating system user identifier.

System Variables Periodically Set/Reset by the Software or the Application System

The values of these variables are set and reset depending on conditions encountered during execution of the application. An application program can assign a value to any of these variables at any time; however, the assigned value can be overwritten as conditions subsequently change during the application session.

Last Callback Event

Event is a data structure that provides information about the application environment the time of the most recent callback even. Each variable in the structure provides one item of information. The values of these variables are reset each time a callback event returns control to the application program. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that a callback event occurs.

Event.AltKey,
Event.CtrlKey,
Event.ShiftKey

The state of the Alt, Ctrl, and Shift keys during the last event.

Event.EventName

The last event to occur.

Event.EventTag

The object in which the last event occurred.

Event.EventType

The type of event that last occurred.

Event.FieldTag

The current field at the time of the last event.

Event.FormTag

The current form at the time of the last event.

Event.KeyPressed

The key that, when pressed, caused the last event to occur.

Event.MenuItemTag

The selected item on the menu in the current window at the time of the last event.

Event.MenuTag

The current menu at the time of the last event.

Event.MouseClick

If a mouse button accelerator caused an event to occur.

Event.ScrollingKey

If an event corresponds to a defined SCROLL key.

Event.WindowTag

The current window at the time of the last event.

Text Cursor Positioning

$CursorCol, $CursorRow

The location of focus in a window when an event occurs.

$CursorScreenCol, $CursorScreenRow

The location of focus on the screen when an event occurs.

$Direction

The direction in which focus was moving when an event occurs.

Error Status

$ErrCode

The error code generated by the last command executed.

$ErrLevel

The error severity level generated by the last command executed.

$LastErrCode

The error code generated by the last command that returned an error code.

$LastErrLevel

The error severity level generated by the last command that returned an error severity level.

$LastErrMessage

The error message generated by the last command that returned an error code.

$MaxErrLevel

The highest error severity level generated during the application session.

$SQLErrCode

The error code returned from the SQL database.

$SQLErrMsg

The error message returned from the SQL database.

Other Status Conditions

$BreakFlag

If the application user has pressed the "break" key.

$DeadlockReason

The reason that a deadlock condition occurred.

$InTransaction

If an explicit transaction is in progress.

$Located

The number of records located by a LOCATE command.

$MemberCount

The number of records processed by a set-processing command.

$Page

The current page number in a report.

$SetCount

The number of records found by the last FIND command.

External Programs

$Editor

The name of a text editor software package.

$Graphics

The name of a graphics software package.

$HelpFile

The name of a disk file containing online help.

Security

$ZGroupID

The application user's Zim group identifier.

$ZUserID

The application user's Zim user identifier.

System Variables Concerned with Windows

Last Event in the Current Window

ThisWindow is a data structure that provides information about the state of the application environment and of the current window at the time of the last event in that window. Each variable in the structure provides one item of information. The values of these variables are reset each time a window becomes the current window. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that another window becomes the current window.

ThisWindow.AltKey,
ThisWindow.CtrlKey,
ThisWindow.ShiftKey

The state of the Alt, Ctrl, and Shift keys at the time of the last event in the current window.

ThisWindow.EventName

The last event that occurred in the current window.

ThisWindow.EventTag

The identification tag of the object in which the last event in the current window occurred.

ThisWindow.EventType

The type of event that last occurred in the current window.

ThisWindow.KeyPressed

The key that, when pressed, caused the event that last occurred in the current window.

ThisWindow.MouseClick

If a mouse button accelerator caused the event that last occurred in the current window.

ThisWindow.ScrollingKey

If the accelerator that caused the event that last occurred was also a defined SCROLL key.

ThisWindow.WindowCol,
ThisWindow.WindowRow

The character column and character row position of the current window.

ThisWindow.WindowHeight,
ThisWindow.WindowWidth

The physical size of the current window in character rows and columns.

ThisWindow.WindowName,
ThisWindow.WindowNum,
ThisWindow.WindowTag

The current window

ThisWindow.WindowState

If the current window is maximized, minimized, or otherwise.

Miscellaneous

$WindowPSHeight, WindowPSWidth

The logical size of the current window in character rows and columns.

System Variables Concerned with Menus

Last Event in the Current Menu

ThisMenu is a data structure that provides information about the state of the software environment and of the current menu at the time of the last event in that menu. Each variable in the structure provides one item of information. The values of these variables are reset each time that FORM or MENU INPUT terminates. An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that FORM or MENU INPUT terminates.

ThisMenu.Menuchanged

If any menu item in the current menu has been modified by the application use at the time of the last event in the current window.

ThisMenu.MenuItemNum,
ThisMenu.MenuItemTag

The selected item on the menu at the time of the last event in the current window.

ThisMenu.MenuNum
ThisMenu.MenuTag

The current menu at the time of the last event in the current window.

System Variables Concerned with Forms

Last Event in the Current Form/Display

ThisForm is a data structure that provides information about the state of the current form/display at the time of the last event in the current window. Each variable in the structure provides one item of information. The values of these variables are reset each time that FROM or MENU INPUT terminates, An application program can assign a value to any of these variables at any time; however, the assigned value is overwritten the next time that FORM or MENU INPUT terminates.

ThisForm.DisplayTag

The display that had focus at the time of the last event in the current window.

ThisForm.FieldChanged

A code indicated if the form field that had focus at the time of the last event in the current window was modified by the application user.

ThisForm.FFFieldNum,
ThisForm.FieldTag

The form field that had focus at the time of the last event in the current window.

ThisForm.FormChanged

A code indicating if any form field in the form or display had been modified by the application user at the time of the last event in the current window.

ThisForm.FormNum,
ThisForm.FormTag

The form that had focus at the time of the last event in the current window.

ThisForm.ReqError,
ThisForm.ReqFieldNum,
ThisForm.ReqFormNum,
ThisForm.ReqSubscript,
ThisForm.ReqTag

If all required form fields had values at the time of the last event in the current window.

ThisForm.Subscript

The instance of the form where focus was located at the time of the last event in the current window.

ThisForm.ValError,
ThisForm.ValFieldNum,
ThisForm.ValFormNum.
ThisForm.ValSubscript,
ThisForm.ValTag

If all form fields contained valid values at the time of the last event in the current window.