The compiler must be able to evaluate the expression in a constant declaration at compile time. This means that most of the functions in the Run-Time library cannot be used in a constant declaration. Operators such as +, -, *, /, not, and, or, div(), mod(), ord(), chr(), sizeof can be used, however. For more information on expressions, You can only declare constants of the following types: Ordinal types, Real types, Char, and String. The following are all valid constant declarations:
Constant declaration
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Const e = 2.7182818; { Real type constant. } a = 2; { Integer type constant. } c = '4'; { Character type constant. } s = 'This is a constant string'; {String type constant.} s = chr(32) ls = SizeOf(Longint);Assigning a value to a constant is not permitted. Thus, given the previous declaration, the following will result in a compiler error:
s := 'some other string';