ตัวอย่าง program ที่ run ได้ -> original ref : http://pantip.com/topic/34834020

calStation.c

#include<stdio.h>
#include<conio.h>
#include<stdbool.h>

 int main()
 {
    char menu;
    int recieved, change, stationPrice;

    do
    {
        system("cls");

        printf (" # THAILAND STATION # \n");
        printf (" 1. Trang = 25 $ \n");
        printf (" 2. BKK = 30 $ \n");
        printf (" 3. Chumporn = 35 $ \n");
        printf (" 4. Chiangmai = 40 $ \n");

        printf("\n");
        printf("Please select station \n");

        printf ("------------------------ \n");
        printf ("You choose station : ");

        menu = getche();

        switch(menu)
        {
            case '1':
                stationPrice = 25;

                printf(" Trang \n");
                printf(" PRICE 25 $ \n");

                do {
                    printf(" You pay : ");

                    scanf("%d", &recieved);
                    change = recieved-stationPrice;

                    if (change < 0) {
                         printf("\n");
                         printf("########################################## \n");
                         printf("You cannot buy this station \n");
                         printf("Please pay at least %d $ \n", stationPrice);
                         printf("########################################## \n");
                         printf("\n");
                    }
                } while (change < 0);

                    printf(" Change = %d \n", change);
                    printf("Thank you for buying^_^ \n");

            break;

            case '2':
                stationPrice = 30;

                printf(" BKK \n");
                printf(" PRICE 30 $ \n");

                do {
                    printf(" You pay : ");

                    scanf("%d", &recieved);
                    change = recieved-stationPrice;

                    if (change < 0) {
                         printf("\n");
                         printf("########################################## \n");
                         printf("You cannot buy this station \n");
                         printf("Please pay at least %d $ \n", stationPrice);
                         printf("########################################## \n");
                         printf("\n");
                    }
                } while (change < 0);

                    printf(" Change = %d \n", change);
                    printf("Thank you for buying^_^ \n");

            break;

            case '3':

                stationPrice = 35;

                printf(" Chumporn \n");
                printf(" PRICE 35 $ \n");

                do {
                    printf(" You pay : ");

                    scanf("%d", &recieved);
                    change = recieved-stationPrice;

                    if (change < 0) {
                         printf("\n");
                         printf("########################################## \n");
                         printf("You cannot buy this station \n");
                         printf("Please pay at least %d $ \n", stationPrice);
                         printf("########################################## \n");
                         printf("\n");
                    }
                } while (change < 0);

                    printf(" Change = %d \n", change);
                    printf("Thank you for buying^_^ \n");


            break;

            case '4':

                stationPrice = 40;

                printf(" Chiangmai \n");
                printf(" PRICE 40 $ \n");

                do {
                    printf(" You pay : ");

                    scanf("%d", &recieved);
                    change = recieved-stationPrice;

                    if (change < 0) {
                         printf("\n");
                         printf("########################################## \n");
                         printf("You cannot buy this station \n");
                         printf("Please pay at least %d $ \n", stationPrice);
                         printf("########################################## \n");
                         printf("\n");
                    }
                } while (change < 0);

                    printf(" Change = %d \n", change);
                    printf("Thank you for buying^_^ \n");

            break;

            default :
                printf("\n No station %c has found. \n", menu);
            break;
       }

       printf("\n");
       printf("Press 'Enter' to re-select the station. \n");
       printf("Press 'q' to quit. \n");

       char userChoice = getch();

       if (userChoice == 'q') {
            printf("\n^_^ See you later ^_^");
            getche();
            return 0;
       }
 } while(true);

 return 0;

 }