C Switch Statement

[prescient63]

This is driving me crazy. Basically, it just skips past the the if statement and doesn't get a character. I'm sure it's something ridiculously simple I'm doing incorrectly.

Welcome to the Grade Calculation Program
Menu
1. Enter Test Grades
2. Enter Quiz grades
3. Enter Homework grades
4. Calculate final grade
5. Quit
Please enter your choice: 1
Are you sure you would like to enter new test scores? Previous values will be er
ased (y or n): Menu
1. Enter Test Grades
2. Enter Quiz grades
3. Enter Homework grades
4. Calculate final grade
5. Quit
Please enter your choice:

Below is the problem code and below that will be all the code. Thanks for any help!

 switch(selection) {
            case 1:
                printf("Are you sure you would like to enter new data? Previous values will be erased (y or n): ");
                yn = getchar();
                if (yn == 'y')
                    {
                    test();
                    }
                break;

#include 
#include 
int selection;
float quiz1, homework1, test1;



int welcome()
{
    printf("Welcome to the Grade Calculation Program\n");
}

int test()
{

    int num1, i;
    float grade, average;
    grade = average = 0;


    printf("How many tests do you have to enter? ");
    scanf("%i", &num1);
    for (i = 1; i <= num1; i++)
    {
        printf("%i. ", i);
        scanf("%f", &grade);
        average = average + grade;
    }
    average = average / num1;
    printf("Test average = %.2f\n\n", average);

    test1 = average;
    return (average);

}

int quiz()
{
    int num1, i;
    float grade, average;
    grade = average = 0;

    printf("How many quizes do you have to enter? ");
    scanf("%i", &num1);
    for (i = 1; i <= num1; i++)
    {
        printf("%i. ", i);
        scanf("%f", &grade);
        average = average + grade;
    }
    average = average / num1;
    printf("Quiz average = %.2f\n\n", average);
    quiz1 = average;
    return (average);
}
int homework()
{
    int num1, i;
    float grade, average;
    grade = average = 0;

    printf("How many homeworks do you have to enter? ");
    scanf("%i", &num1);
    for (i = 1; i <= num1; i++)
    {
        printf("%i. ", i);
        scanf("%f", &grade);
        average = average + grade;
    }
    average = average / num1;
    printf("Homework average = %.2f\n\n", average);
    homework1 = average;
    return (average);
}
int menu()
{
    printf("\tMenu\n");
    printf("1. Enter Test Grades\n2. Enter Quiz grades\n3. Enter Homework grades\n4. Calculate final grade\n5. Quit\n");
    printf("Please enter your choice: ");
}

int scan()
{
    scanf("%i", &selection);
    return(selection);
}

int final()
{
    float quiz, homework, test, final;


    final = .5 * test1 + .3 * quiz1 + .2 * homework1;
    printf("\nFinal Grade: %f.0\n\n", final);

}
int quit()
{
    printf("Thank you. Have a great day!\n\n");
}

int main()
{
char yn;



    welcome();

    do {
        menu();
        scan();

        switch(selection) {
            case 1:
                printf("Are you sure you would like to enter new test scores? Previous values will be erased (y or n): ");
                yn = getchar();
                if (yn == 'y')
                    {
                    test();
                    }
                break;
            case 2:
                quiz();
                break;
            case 3:
                homework();
                break;
            case 4:
                final();
                break;
            case 5:
                quit();
                break;
            default:
                printf("That is an invalid entry please try again.");
                break;
        }
    }while (selection != 5);
}

[Tenks]

My only assumption is int selection is not being properly set. Does it only fail on case 1 or does it fail on every case?

If it fails for everything then I don't understand why selection is global to begin with in the first place. It's scope should be reduced to only the main() method.

 int selection = scan();
 switch(selection) {
            case 1:
                printf("Are you sure you would like to enter new data? Previous values will be erased (y or n): ");
                yn = getchar();
                if (yn == 'y')
                    {
                    test();
                    }
                break;

[prescient63]

Originally Posted by Tenks

My only assumption is int selection is not being properly set. Does it only fail on case 1 or does it fail on every case?

If it fails for everything then I don't understand why selection is global to begin with in the first place. It's scope should be reduced to only the main() method.

 int selection = scan();
 switch(selection) {
            case 1:
                printf("Are you sure you would like to enter new data? Previous values will be erased (y or n): ");
                yn = getchar();
                if (yn == 'y')
                    {
                    test();
                    }
                break;

If I pull out the if statement the program works fine, and yes there is no need for the selection statement to be global. The selection will only fail for case 1. It has something to do with the If statement but i cant figure it out for the life of me.

[Araex]

The getchar() is returning the leftover newline character from the previous input.

You can substitute the getchar() line with something like

do {yn = getchar();} while (yn <= 32);

to filter the newline and whitespace characters.

P.S. Disclaimer, this is just a quick fix/hack to your program, and not how I would do it

[Zuuljin]

nm thats probably it. =)

[Tenks]

Is the issue getchar() does not set yn to a proper variable? I am not a C programmer by any stretch but from my quick google search it appears like getchar() is used to read a single char from a file and you may want to just use a scanf here.

-edit-

nm looks like a real C programmer answered

[prescient63]

Originally Posted by Araex

The getchar() is returning the leftover newline character from the previous input.

You can substitute the getchar() line with something like

do {yn = getchar();} while (yn <= 32);

to filter the newline and whitespace characters.

P.S. Disclaimer, this is just a quick fix/hack to your program, and not how I would do it

Awesome thanks! I doubt anyone who has any clue what they were doing would do any of this program like I did

Edit: Props to everyone for the help!