CODEWITHSUNDEEP
cloops
Sofia Lazrak
Sofia Lazrak

Reputation: 314

Prompting user for input until newline and checks if input is valid

This program prompts the user for quiz grades and store them in an array. The user can enter a maximum of 10 grades, but can enter less. The program should error-check: if the user enters an invalid grade, the program should loop until the user correctly enters a valid grade

    #include <stdio.h>
    #define N 10 /* number of students in class */
    int main()
    {
        int quiz[N], /* array of quiz grades */
        grade, /* used to read in one grade */
        last, /* index of last element used */
        i, /* loop variable */
        ib /* input buffer */;
        char c;
        
        last = -1;
     
        printf("Enter the quiz grade: ");
       
        while (ib=scanf("%d",&grade) && last<N-1)
        {
             
            if(ib == 0 ){
                printf("Please enter a valid quiz grade: ");
                while((c=getchar())!='\n' && c!=EOF);
            }
            else 
                if(grade >= 0 && grade <= 10)
                {
                    last++;
                    quiz[last] = grade;
                }
                else{
                    printf("Enter a quiz grade between 0 and 10");
                }
        }
    }

This code does not stop at the number of grades entered but rather fills the array with the last grade until its size is N.

Also when the user enter a non digit input the program stops when it should prompt the user to enter a valid grade

Upvotes: 0

Views: 41

Answers (1)

4386427
4386427

Reputation: 44340

At least one bug is here:

while (ib=scanf("%d",&grade) && last<N-1)

Assume that scanf returns zero (i.e. ib becomes zero) then the above is the same as:

while (0 && last<N-1)

which is the same as

while (0)

which means that your loop stops when something not being a number is entered.

Also notice that due to the above, ib can not be zero when you execute:

        if(ib == 0 ){
            // So this code can't be reached
            printf("Please enter a valid quiz grade: ");
            while((c=getchar())!='\n' && c!=EOF);
        }

To solve this you can move the scanf out of the while condition. Like:

    while (last<N-1)
    {
        ib=scanf("%d",&grade);
        if(ib != 1 )            // Notice this change
        {
            if (ib == EOF) exit(1);  // Check for fatal input error

            printf("Please enter a valid quiz grade: ");
            while((c=getchar())!='\n' && c!=EOF);

            if (c == EOF) exit(1);  //  Check for fatal input error
        }
        else 
        {
            ...
        }
     }

Also change char c; to int c; as getchar returns an int in order to handle EOF

Upvotes: 2

Related Questions