Question

int main() char in, Cls; int r-0; printf("A: Circle nB: Square\nC: Triangle\n"); printf("Enter Which Shape to use: \n"); scanf("%c", &in); switch(in) [ case A' printf("Enter P for solve for perimeter and A for solve for Area\n"); printf("Choice: "); scanf(%c", &cis); / /cis is choice printf("Enter circle radius: "); scanf("%lf", &r); printf("Circle perimeterr is:", perimeter('A', 2, 0, e)); return 0;

Why when i enter A, and the second scanf founction is not work, there are no value for cis.

Answer 1

The scanf does not work because in the first scanf i.e.

scanf("%c", &in);

Here you type a character and press enter.

The scanf will assign the character you typed to 'in' variable but the enter i.e. the newline character is left behind.

So when you try to scan another character 'cis' - scanf("%c", &cis); - the newline character from the previous scanf will be consumed automatically, which gives rise to the problem you are facing.

There are two ways to rectify the error

1) Use a getchar() after the first scanf() to consume the newline character.

#include <stdio.h>

int main()

{

    // Variable declaration

    char in, cis;

    int r = 0;

   

    // Display menu

    printf("A: Circle\nB: Square\nC: Triangle\n");

    printf("Enter which shape to use:\n");

    scanf("%c", &in);

    // Consume the newline character from the above scanf

    getchar();

   

    switch(in) {

        case 'A':

        printf("Enter P for solve for perimeter and A for solve for Area\n");

        printf("Choice: ");

        scanf("%c", &cis); // cis is Choice

        // scanf(" %c", &cis); // cis is Choice

        if(cis == 'P') {

            printf("Enter circle radius: ");

            scanf("%d", &r);

           

            // Rest of the code

            // ...

        }

    }

    return 0;

}

SAMPLE OUTPUT:

2) Use a <space> in the second scanf statement - scanf(" %c", &cis);

#include <stdio.h>

int main()

{

    // Variable declaration

    char in, cis;

    int r = 0;

   

    // Display menu

    printf("A: Circle\nB: Square\nC: Triangle\n");

    printf("Enter which shape to use:\n");

    scanf("%c", &in);

    // Consume the newline character from the above scanf

    // getchar();

   

    switch(in) {

        case 'A':

        printf("Enter P for solve for perimeter and A for solve for Area\n");

        printf("Choice: ");

        // scanf("%c", &cis); // cis is Choice

        scanf(" %c", &cis); // cis is Choice

        if(cis == 'P') {

            printf("Enter circle radius: ");

            scanf("%d", &r);

           

            // Rest of the code

            // ...

        }

    }

    return 0;

}

SAMPLE OUTPUT:

A: Circle B: Square C: Triangle Enter which shape to use: Enter P for solve for perimeter and A for solve for Area Choice: P Enter circle radius: 45