The document discusses variable argument functions in C. It explains that variable argument functions allow a function to take a variable number of arguments. It provides examples of common variable argument functions like printf and scanf. It then describes how to create a variadic function using the stdarg.h header file and macros like va_list, va_start, va_arg, and va_end. Finally, it provides examples of functions that find the minimum and average of a variable number of input arguments.

1. R.Ramya

2. Variable argument functions
 Most common variable argument functions are
 void printf(const char* fmt, …);
 void scanf(const char* fmt, …);
 Parameters include
 One named argument usually a format string
 Ellipsis indicating the function may take any number of
arguments and their types

3. Creating a Variadic Function
 Use standard header - stdarg.h
 4 macros are needed from this header file
 va_list
 va_start
 va_arg
 va_end

4. Variable arguments in C
 va_list
 Datatype to store the list of arguments
 Declared like any other variable
 Ex. va_list ap;
 va_start
 initializes ap variable to be used with the va_arg and
va_end macros
 Accepts two arguments
 va_list
 Name of the variable that directly precedes the ellipsis
 Ex: va_start(ap, count);

5. Variable arguments in C
 va_arg
 returns the next argument of whatever type it is told
 moves down to the next argument in the list
 Accepts two arguments
 va_list
 Variable argument type
 Ex. va_arg(ap, int); //returns next int value in the argument
 va_end
 Cleans up the variable argument list
 Ex. va_end(ap);

6. To find minimum of ‘n’ numbers
#include <stdarg.h>
#include <stdio.h>
int min(int arg_count, ...)
{
int i; int min, a;
va_list ap;
va_start(ap, arg_count);
min = 9999;
for (i = 1; i <= arg_count; i++)
if ((a = va_arg(ap, int)) < min)
min = a;
va_end(ap);
return min;
}

7. To find minimum of ‘n’ numbers (Contd)
// Driver code
int main()
{
int count = 5;
printf("Minimum value is %d",
min(count, 12, 67, 6, 7, 100));
return 0;
}

8. To find average of ‘n’ numbers
#include <stdio.h>
#include <stdarg.h>
double average ( int num, ... )
{
va_list ap;
double sum = 0;
va_start ( ap, num ); //initializes, store all values
int x;
for ( x = 0; x < num; x++ )
sum += va_arg ( ap, double );
va_end ( ap );
return sum/num;
}
int main()
{
printf( "%fn", average ( 3, 12.2, 22.3, 4.5 ));
printf("%fn", average ( 5, 3.3, 2.2, 1.1, 5.5, 3.3 ));
return 0;
}