I just started using keil c51 compiler. Since I know that keil is compatible to ANSI-C I want to know if there is an ANSI-C compatible notation for binary numbers. Like when I want to write the number in hexadecimal notation I use the prefix "0x" -> 0xFF All oher numbers are considered to be in decimal notation. -> 1234567890 But which prefix do I use for binary number system? I already tried (0b..., ...b, ...) and got ->error C251: illegal octal digit ->error C141: syntax error near 'b' ... By the way, it would be nice to know which notation to use for octal number systems. Regards J.