Is the 'C' language acting differently for all the SDK(VisualStudio,xCode...)?

Question

Hi guys~!
I've been in a dazed since i started writing this piece of code as an example since i'm still learning 'C' programming in the Poly's. Is the 'C' language acting differently while is on another platform?
When i wrote this using VS, it works, but when it comes to Xcode, it's not going to provide me the right output.
#include <stdio.h>
#include <ctype.h>
int main(int argc, const char * argv[])
    int x, num = 0;
    char choice;
    printf("Number\n");
    for (choice = 'Y'; choice == 'Y'; num++)
        for (x = 1; x <= 4; num++)
            printf("%6d\n", x);
            x++;
        } // end for
        printf("\nWould you like to continue the loop? Y/N?: ");    < - - It ignored the user key and skipped out of the loop, and proceed with the final output.
        fflush(stdin);
        scanf("%c", &choice);
        choice = toupper(choice);
    } // end for
    printf("Thank you for your participation~! Have a nice day & See you!");
} // end main

Answer 1

Code the scanf like this:
scanf(" %c", &choice);
Note the leading white space.
c
Matches a sequence of width count characters (default 1); the next pointer must
be a pointer to char, and there must be enough room for all the characters (no
terminating NUL is added).  The usual skip of leading white space is sup-
pressed.  To skip white space first, use an explicit space in the format.