Just use the standard C syntax; remember, Objective-C is a strict superset of C.
.hWrite an ad in the file
extern return_type function_name(argument_type1 argument_name1,argument_type2 argument_name 2);
.m ( .c - ),
return_type function_name(argument_type1 argument_name1,argument_type2 argument_name 2){
....
}
.m, @implementation ... @end. (, , .) !