The first line contains the number of points, then the coordinates of the points are entered afterwards separated by white space (it is easiest to understand the file if you have the x and y coordinates of a point on the same line separated by a blank space with just one point per line).
int main (int argc, char * argv)The parameter argc will contain the number of arguments passed to main when the program is called and argv is an array of the arguments. The first argument is the name of the executable and is in position 0 of the array (argv[0]).
The example commandArg.cc reads a list of numbers from a file and partitions them using just the first step of the quicksort algorithm. The file command1.in is a test file. Study this example and the earlier file IO example (earlier lab). Your program needs to also have the output file name passed in at the command line.