ObjectPascal Nil Constant A pointer value that is defined as undetermined System unit

const Nil = Pointer(0);

Description The Nil constant is a pointer value that is defined as undetermined.   Use of a Nil pointer will result in an exception.   Nil is mostly used as a substitute for a Pointer parameter - it tells the routine that no Pointer value is available for this parameter.   Pointer variables are not set to Nil except in special circumstances, such as when creating a new object that contains pointers. This is because Delphi initialises the storage taken by a new object to 0's. A Nil pointer is one that has the value 0. Related commands Assigned Returns true if a reference is not nil Null A variable that has no value Pointer Defines a general use Pointer to any memory based data		Example code : A simple example var   myPtr : PChar; begin   // Pointer variables are not set to nil by default   if myPtr = Nil   then WriteLn('myPtr is nil')   else WriteLn('myPtr is not nil');   // So we must set them to nil to be sure that they are undefined   myPtr := Nil;   if myPtr = Nil   then WriteLn('myPtr is nil')   else WriteLn('myPtr is still not nil'); end; Show full unit code    myPtr is not nil    myPtr is nil