Greek Capital Letter Iota
HTML Entity Browser Test:

U+0399 is the Unicode hex value of the character Greek Capital Letter Iota, which is categorized as "uppercase letter" in the Unicode 6.0 character table.

Unicode Character Information
Unicode Hex U+0399
General Category Uppercase Letter [Code: Lu]
Canonical Combining Class 0
Bidirectional Category L
Mirrored N
Lowercase Version U+03B9
Unicode Character Encodings
Greek Capital Letter Iota HTML Entity Ι (decimal entity), Ι (hex entity)
Windows Key Code Alt 0921 or Alt +03991
Programming Source Code Encodings Python hex: u"\u0399", Hex for C++ and Java: "\u0399"
UTF-8 Hexadecimal Encoding 0xCE99
1 To type a Unicode symbol in Windows, hold down the ALT key and enter the decimal or hexadecimal code provided using the numeric keypad. The decimal alt code (Alt 0921) will only work on computers with support for this Unicode character in the active code page. The hexadecimal alt code (Alt +0399) will work for all Unicode characters provided Hex input from the numeric keypad is enabled.
* If the Greek Capital Letter Iota character does not display correctly in your browser, you may not have a Unicode font on your system that supports this particular symbol.