ToCharacterCode

ToCharacterCode["string"] gives a list of the integer codes corresponding to the characters in a string.

ToCharacterCode["string", "encoding"] gives integer codes according to the specified encoding.

Examples

Get character codes:

ToCharacterCode["Hello"]
(* {72, 101, 108, 108, 111} *)

Single character:

ToCharacterCode["A"]
(* {65} *)

Please visit the official Wolfram Language Reference for more details.