How to use toupper(),strcat(),strcpy() built in functions in C programming!

 #include <stdio.h>

#include <stdlib.h>

#include <ctype.h>

#include <string.h>

#include <math.h>

int main()

{

    char a = 'b';

    printf("%c \n",toupper(a));

    char noodles [100] = "hey," ;

    strcat(noodles,"Mashrafe.");

    strcat(noodles,"You ");

    strcat(noodles,"Good?");

    printf("%s \n",noodles);

    strcpy(noodles,"I'm Fine!");

    printf("%s \n",noodles);

    return 0;

}