Where does (char)int get its symbols from?

Question

Being a computer programming rookie, I was given homework involving the use of the playing card suit symbols. In the course of my research I came across an easy way to retrieve the symbols:

 Console.Write((char)6);

gives you ♠

  Console.Write((char)3);

gives you ♥

and so on...

However, I still don't understand what logic C# uses to retrieve those symbols. I mean, the ♠ symbol in the Unicode table is U+2660, yet I didn't use it. The ASCII table doesn't even contain these symbols.

So my question is, what is the logic behind (char)int?

Answer 1

For these low numbers (below 32), this is an aspect of the console rather than C#, and it comes from Code page 437 - though it won't include the ones that have other meanings that the console actually uses, such as tab, carriage return, and bell. This isn't really portable to any context where you're not running directly in a console window, and you should use e.g. 0x2660 instead, or just '\u2660'.

Answer 2

The logic behind (char)int is that char is a UTF-16 code unit, one or two of which encode a Unicode codepoint. Codepoints are naturally ordinal numbers, being an identifier for a member of a character set. They are often written in hexadecimal, and specifically for Unicode, preceded by U+, for example U+2660.

UTF-16 is a mapping between codepoint and code units. Code units being 16 bits can be operated on as integers. Since a char holds one code unit, you can convert an short to a char. Since the different integer types can interoperate, you can convert an int to a char.

So, your short (or int) has meaning as text only when it represents a UTF-16 code unit for a codepoint that only has one code unit. (You could also convert an int holding a whole codepoint to a string.)

Of course, you could let the compiler figure it out for you and make it easier for your readers, too, with: Console.Write('♥');

Also, forget ASCII. It's never the right encoding (except when it is). In case it's not clear, a string is a counted sequence of UTF-16 code units.