4th Dimension (software)

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In Standalone mode, the 4D application (4D.exe on Windows or 4D.app on Mac) is used to open the structure file (4DB/4DC) file directly along with the associated data file (4DD).

In the Client-Server paradigm the 4D Server application (4DServer.exe on Windows or 4DServer.app on Mac) is used to open the structure file (4DB/4DC) file directly along with the associated data file (4DD). 4D may then be used in remote mode to connect to the 4D Server.

4D can be run in two modes. 4D in single-user mode allows for 1 person to run the application. 4D in remote mode is used for connecting to a 4D Server.

4D Server is used for Client-Server connectivity to the application. In this mode, 4D Server loads the structure file (4DB or 4DC) and also the datafile (4DD) and provides network access to 4D (in remote). Each workstation has a dynamically updated cache of the resources they are working with, while the 4D Server maintains the data and code.

4D fields, variables, and expressions can be of the following data types:[18]

More info on 4D data type can be found on the [ 4D Data Types] documentation page

Local variables are prefixed with a $ like $myLocalVariable and only live for the duration of the method.

Process variables have no prefix like myProcessVariable and live throughout the duration of the process.

Inter-process (or Global) variables are prefixed with a <> like <>myGlobalVariable and live throughout the duration of the application.

For(vCounter;1;100)
  // Do something
End for

 $i :=1 // Initialize the counter
 While($i<=100) // Loop 100 times
  // Do something
    $i :=$i +1 // Need to increment the counter
 End while

 $i :=1 // Initialize the counter
 Repeat
  // Do something
    $i :=$i +1 // Need to increment the counter
 Until($i=100) // Loop 100 times

The following example goes through all the elements of a two-dimensional array:

 For($vlElem;1;Size of array(anArray))
  // ...
  // Do something with the row
  // ...
    For($vlSubElem;1;Size of array(anArray{$vlElem}))
       // Do something with the element
       anArray{$vlElem}{$vlSubElem}:=...
    End for
 End for

The following example builds an array of pointers to all the date fields present in the database:

 ARRAY POINTER($apDateFields;0)
 $vlElem:=0
 For($vlTable;1;Get last table number)
   // loop over each table number with $vTable as the number
    If(Is table number valid($vlTable))
      // check if table number $vTable is valid
      // only loop on the valid table
       For($vlField;1;Get last field number($vlTable))
         // loop over each field number within current table
         // with $vlField as the current field number
          If(Is field number valid($vlTable;$vlField))
            // check if field number is valid
             $vpField:=Field($vlTable;$vlField) // get pointer to field
             If(Type($vpField->)=Is date)
               // check if current field is a date
               // only performs these actions if field is a date
                $vlElem:=$vlElem+1
                INSERT IN ARRAY($apDateFields;$vlElem)
                $apDateFields{$vlElem}:=$vpField
             End if
          End If
       End for
    End If
 End for