‎#include is a header file which enables us to pass multiple arguments to a function.You can pass multiple arguments by using "..." after d last variable. for eg: avg(int num,...); so this function avg(int num,...) vil take variable no of arguments and 1 integer arguments for num. it has 1 type : va_list to hold info abt variable arguments and 3 functions 1. va_start 2. va_arg 3. va_end va_start is used to start iterating by passing it 2 arguments : an object of type va_list and second parameter is d last named parameter of d function for eg: avg(int num,...) den va_list l; va_start(l,num); //dis initializes d list of variable arguments now to use individual arguments we use va_arg() it accepts va_list as first argument and type of d argument in the list. i.e va_arg(l,int); it returns d arguments in d same order in which dey were passed to the function...!! when we r done we use va_end to free d memory used by our list. In c it is mandatory to give 1 normal parameter but in c++ its nt mandatory....!!