CODEWITHSUNDEEP
c
user2625486
user2625486

Reputation: 157

It prints The printf statement twice

This is really strange it prints this line printf("Do you want to continue Yes (Y) or No (N): \n"); Not using any loop nothing but still it prints that statement twice

int main()
{

int led=0;
int ohm=0;
char check;
int flag=0;

while (led < 1 || led > 3){
    printf("Enter the number of switch you want to close: \n\n");
    printf("  ********************     Press 1 for switch (LED) 1     ********************\n");
    printf("  ********************     Press 2 for switch (LED) 2     ********************\n");
    printf("  ********************     Press 3 for switch (LED) 3     ********************\n");

    printf("Switch: ");
    scanf("%d", &led);
}

printf("\n\n");
while (ohm < 1 || ohm > 3){
    printf("Enter the resistance of Rheostat: \n\n");
    printf("  ********************     Press 1 for 10 ohm resistance  ********************\n");
    printf("  ********************     Press 2 for 20 ohm resistance  ********************\n");
    printf("  ********************     Press 3 for 30 ohm resistance  ********************\n");

    printf("Resistance: ");
    scanf("%d", &ohm);
}


    while (flag == 0)
    {
        //LED-1
        if(led== 1 && ohm== 1 )
        {
            printf("LED-1 is blinking 2 times\n");
        }

        if(led== 1  && ohm== 2)
        {
            printf("LED-1 is blinking 4 times\n");
        }

        if(led== 1  && ohm== 3 )
        {
            printf("LED-1 is blinking 6 times\n");
        }

        //LED-2
        if(led== 2  && ohm== 1 )
        {
            printf("LED-2 is blinking 2 times\n");
        }

        if(led== 2  && ohm== 2 )
        {
            printf("LED-2 is blinking 4 times\n");
        }

        if(led == 2  && ohm == 3)
        {
            printf("LED-2 is blinking 6 times\n");
        }

        //LED-3
        if(led == 3  && ohm == 1 )
        {
            printf("LED-3 is blinking 2 times\n");
        }

        if(led == 3  && ohm == 2)
        {
            printf("LED-3 is blinking 4 times\n");
        }

        if(led == 3 && ohm == 3)
        {
            printf("LED-3 is blinking 6 times\n");
        }

        led = 0;
        ohm = 0;
        printf("Do you want to continue Yes (Y) or No (N): \n");
        scanf("%c", &check);

        if(check =='Y' || check =='y')
        {

            while (led < 1 || led > 3){
            printf("Enter the number of switch you want to close on: ");
            scanf("%d", &led);
            }

            while (ohm < 1 || ohm > 3){
            printf("Enter the resistance of Rheostat: ");
            scanf("%d", &ohm);
            }
        }

        if(check=='N' || check=='n')
        {
            printf("Thanks for using the program");
            flag = 1;
        }



    }
    return 0;

}

Upvotes: 1

Views: 16435

Answers (5)

Antonio
Antonio

Reputation: 20256

The first time scanf("%c", &check); finds some garbage (that does not match y or n) so your program can do another loop.

As someone else already noticed, that garbage might be the newline after the ohm input.

Some ideas to solve the problem:
http://www.velocityreviews.com/forums/t436518-get-rid-of-trailing-newline-for-scanf.html

scanf(" %c", &input);

(leading space will eat whitespace in the input)


scanf() leaves the new line char in the buffer

Upvotes: 3

Allen Job
Allen Job

Reputation: 46

Use scanf(" %d", &led); , scanf(" %c", &check); etc. in the code. Adding an extra space before the format specifier will solve the problems caused by garbage/newline in the buffer.

Upvotes: 3

No Idea For Name
No Idea For Name

Reputation: 11577

use getchar and it works just fine, you can try it here

Upvotes: 0

Dayal rai
Dayal rai

Reputation: 6606

Please try scanf("%c ", &check);. Notice the extra space given after %c which will absorb extra new line character.

Upvotes: 0

Yu Hao
Yu Hao

Reputation: 122373

scanf("%d", &ohm);

Here when you input a number and press ENTER, the number is processed by scanf, but the newline is still in the input buffer, then later

printf("Do you want to continue Yes (Y) or No (N): \n");
scanf("%c", &check);

check will actually store the newline, not 'N', 

if(check=='N' || check=='n')
{
    printf("Thanks for using the program");
    flag = 1;
}

so flag will not be set to 1, the while loop will continue again. In the second loop, check can be assigned 'N', the loop will terminate after.

Upvotes: 0

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