please help what this ":" command means

Could you please explain what this ":" command means.

int8_t rtr : 1;

thank you.

Used in a structure, it defines a bit-field. That particular example defines rtr to be a single bit, assuming it is part of a structure.

http://en.wikipedia.org/wiki/C_syntax#Bit_fields http://publib.boulder.ibm.com/infocenter/macxhelp/v6v81/index.jsp?topic=%2Fcom.ibm.vacpp6m.doc%2Flanguage%2Fref%2Fclrc03defbitf.htm