Message: The string literal <literal> contains characters that cannot be displayed. The project option 'UTF-8 encoding for STRING' could be used.

Possible error cause: Input of unknown characters which cannot be transformed to Latin-1.

PROGRAM PLC_PRG
VAR
	str1: STRING(200);
	str2: STRING := '1 €';
	str3: STRING(200) := ' !$"#$$%&$'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~';
END_VAR

str1 := '你好,世界';
str1 := 'ABC abc 123 äöü ß#~=" §% /(!)[]{}\ ´`^*~°€µ  *_-.;  中文字 Ω �';
str1 := '1 £';
str1 := '1 €';
str1 := ' !$"#$$%&$'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_`abcdefghijklmnopqrstuvwxyz{|}~';

Message:

C0555: The string literal '你好,世界' contains characters that cannot be displayed. The project option 'UTF-8 Encoding for STRING' could be used.

Error correction: Select the option.