My program skip getting input data? [duplicate]

Question

This question already has answers here:

Simple C scanf does not work? [duplicate] (5 answers)

Closed 6 years ago.

I have written a simple program to exchange currency and able to buy a beer.

But there something in program and I don't know why, it auto skips the third input data -> end program.

Here my code :

#include <stdio.h>
#include <stdlib.h>

int main()
{
    int ex_rate_into_vnd = 20000; //! Exchange Rate
    int beer = 7000; //! Local price of a beer
    float in_c = 0; //! Input amount of money
    float out_c = 2; //! Amount of currency to exchange !
    float choice; //! Switch mode
    char buy; //! Deal or not

    //! Introduction
    printf ("||---------------------------------------------------||\n");
    printf ("||         Currency Exchange Machine  beta           ||\n");
    printf ("||---------------------------------------------------||\n");

    printf ("Please choose your option:\n");
    printf("\t 1.Exchange VND to dollar\n");
    printf("\t 2.Exchange Dollar to VND\n");

    do
    {
        printf("Your choice: ",choice);
        scanf("%f",&choice);
    } while( choice != 1 && choice != 2);

    printf ("Please enter amount of money:");
    scanf("%f",&in_c);

    if (choice == 1 )
        {
            out_c = in_c / ex_rate_into_vnd;
            printf ("Your amount of money: %.2f",out_c);
        }
    else
        {
           out_c = in_c * ex_rate_into_vnd;
           printf ("Your amount of money: %.0f",out_c);
        }
//! End of Exchanging

    printf ("\nWould you like to buy a beer (y/n) ?",buy);
    scanf("%c", &buy);

    if (buy == 'y')
        {
        if (out_c >= 7000)
            {
                out_c = out_c - 7000;
                printf("Transactions success !\n");
                printf("Your amount: %2.f",out_c);
            }
        }
    printf ("\nWhy Stop ?");


    return 0;
}

Answer 1

I was wondering why you made 'choice' a float, not an int Also, consider using a switch-case that way, you won't have to do the whole do-while loop. Also, in the line printf ("\nWould you like to buy a beer (y/n) ?",buy); Why did u add that? Here is what I would have done :

printf("Your choice?\n>");
scanf("%d", &choice);

switch(choice)
{
     case 1 :
    {
         out_c = in_c / ex_rate_into_vnd;
            printf ("Your amount of money: %.2f",out_c);


    }

     case 2:
    {

    out_c = in_c * ex_rate_into_vnd;
           printf ("Your amount of money: %.0f",out_c);

    }

    default :
    printf("\nThere has been an error\n"):
    reloadprogram();   /* Reloadprogram() is simply to make this go back to the asking thing :) */

}

}

EDIT: also, where it says if( <somevariable> >= 7000), change 7000 to beer, so that way, if u change beer, you won't have to change this :)

Answer 2

Instead of scanf("%c", &buy);

1.use space before %c

scanf(" %c",&buy); //space before %c  
       ^ 

this skips reading of white space (including newlines).

2.or Use getchar(); before scanf("%c", &buy); statement

getchar(); //this hold the newline 
scanf("%c", &buy);

3.or use two times getchar();

getchar();
buy=getchar();     
//here getchar returns int , it would be better if you declare buy with integer type.

In GCC usage of fflush(stdin); is discouaraged. please avoid using it.

Answer 3

Put a fflush(stdin) to clear the input before the last scanf

Answer 4

Change

scanf("%c", &buy);

to

scanf(" %c", &buy);
//     ^space

Because the newline character is still in the input buffer after you enter a number and press ENTER in the second scanf.

Answer 5

you can remove the buy variable from the printf call, it's unneeded

printf ("\nWould you like to buy a beer (y/n) ?",buy);

And replace char buy by char buy[2]; . because a sting is always terminated by /0.

You can also add a memset (buy, 0, sizeof(buy)), to be sure that memory is reset before you start to use it.

Answer 6

You have at least one \n between the latest float entry and the char you want to read. You need to get rid of that first.

See also all answers in getchar after scanf category