what is the syntax to define a string constant in assembly?

Question

I am learning assembly I see two examples of defining a string:

msg db \'Hello, world!\',0xa

• what does the 0xa mean here?

message DB \'I

Answer 1

0xa stands for the hexadecimal value "A" which is 10 in decimal. The Linefeed control character has ASCII code 10 (Return has D hexadecimal or 13 decimal).

Strings are commonly terminated by a nul character to indicate their end.