Question

Would you tell me if there is some advantage (less sotorage space, increase speed, etc) in using:

resourcestring
    MsgErrInvalidInputRange = 'Invalid Message Here!';

instead of

const
    MsgErrInvalidInputRange : String = 'Invalid Message Here!';

Answer 1

As others have mentioned, resourcestring strings will be included in a separate resource within your exe, and as such have advantages when you need to cater for multiple languages in the UI of your app.

As some have mentioned as well, const strings are included in the data section of your app.

Up to D2007

In Delphi versions up to D2007, const strings were stored as Ansi strings, requiring a single byte per character, whereas resource strings would be stored in UTF-16: the windows default encoding (though perhaps not for Win9x). IIRC D2007 and prior versions didn’t support UTF-8 encoded unit files. So any strings coded in your sources would have to be supported by the ANSI code pages, and as such probably didn’t go beyond the Unicode Basic Multilingual Plane. Which means that only the UCS-2 part of UTF-16 would be used and all strings could be stored in two bytes per character.

In short: up to D2007 const strings take a single byte per character, resource strings take two bytes per character.

D2009 and up

Delphi was unicode enabled in version D2009. Since then things are a little different. Resourcestring strings are still stored as UTF-16. No other option here as they are “managed” by Windows.

Consts strings however are a completely different story. Since D2009 Delphi stores multiple versions of each const string in your exe. Each version in a different encoding. Const can be stored as Ansi strings, UTF-8 strings and UTF-16 strings.

Which of these encodings is stored depends on the use of the const. By default UTf-16 will be used, as that is the default internal Delphi encoding. Assign the same const to a “normal” (UTF-16) string, as well as to an AnsiString variable, and the const will be stored in the exe both UTF-16 and Ansi encoded…

De-duping

By the looks of it (experimenting with D5 and D2009), Delphi “de-dupes” const strings, whereas it doesn’t do this for resourcestring strings.