Ποια είναι η λειτουργία του ακόλουθου προγράμματος;

            #include <stdio.h>

            #include <ctype.h>

            void conv(char *ps);

            main()

            {

                        char string[]="characters and numbers";

                        printf("The string before conversion is: %s", string);

                        conv(string);

                        printf("\nThe string after conversion is: %s\n", string);

            }

            void conv(char *ps)

            {

                        while (*ps!= '\0')

                        {

                                    if (islower(*ps))            *ps=toupper(*ps);

                                    ++ps;

                        }

            }