Delphi Language Guide Delphi for Microsoft Win32 Delphi for the Microsoft. Net framework

Boolean
ByteBool, WordBool, LongBool
False < True
False <> True
Ord(False) = 0
Ord(False) = 0
Ord(True) = 1
Ord(True) <> 0
Succ(False) = True Succ(False) = True
Pred(True) = False Pred(False) = True
A value of type ByteBool, LongBool, or WordBool is considered True when its ordinality is nonzero. If such a value
appears in a context where a Boolean is expected, the compiler automatically converts any value of nonzero
ordinality to True.
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The previous remarks refer to the ordinality of Boolean values, not to the values themselves. In Delphi, Boolean
expressions cannot be equated with integers or reals. Hence, if X is an integer variable, the statement
if X then ...;
generates a compilation error. Casting the variable to a Boolean type is unreliable, but each of the following
alternatives will work.
if X <> 0 then ...; { use longer expression that returns Boolean value }
          
var OK: Boolean;
 ...
if X <> 0 then OK := True;
if OK then ...;