My code repeats more than requried while loop

Question

The problem is that when i type any character except for y or n it display this message two times instead to one)

This program is 'Calculator'
Do you want to continue?
Type 'y' for yes or 'n' for no 
invalid input 

---

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

void main ()
{
//program
//first to get two numbers 
//second to get choice

int x=0,y=0,n=0;
char choice;

//clrscr(); does no work in devc++
system("cls"); //you may also use system("clear");

while(x==0)
{

    puts("\t\tThis program is 'Calculator'\n\n");
    puts("Do you want to continue?");
    puts("Type 'y' for yes or 'n' for no ");
    scanf("%c",&choice);
    x++;



    if(choice=='y')
    {
        y++;
        puts("if this worked then we would continue to calculate the 2 no");
    }
    else if(choice=='n')
        exit(0);
    else
    {
        puts("invalid input");
        x=0;
    }


    }
getch();

    }

`

Answer 1

If you input any character other than 'y' or 'n', control enters the :

else
{
    puts("invalid input");
    x=0;
}

block, which resets x to 0, Now the loop condition :

while(x == 0)

is true and hence it enters the loop again.

Also you may want to skip the trailing newline character while reading like :

scanf(" %c", &choice );

Answer 2

it looping twice because enter(\n) character is stored in buffer use scanf like this(add space before %c)

scanf(" %c",&choice);

Answer 3

That is because of the trailing new line after you enter y or n and hit enter key.

Try this out:

scanf("%c",&choice);
while(getchar()!='\n'); // Eats up the trailing newlines