CODEWITHSUNDEEP
c
blackthorn
blackthorn

Reputation: 45

Issue with "grading" exercice from C programming language textbook, Joy of C

I try to code with the given code from C programming language textbook, Joy of C, I typed exactly according to the book. This code seem perfect to me and it works fine, except at avg_score which won't compute and display correctly.

It's always displayed 0, so I think the problem might be caused by

total_score = total_score + next_score;

doesn't work properly.

I would like to thank in advance for anybody who give me a hand, especially who know what the cause is.

edit1. I sorry very much for my mistake. I intend to ask for avg_score, not total score. I did check the cause and it appear to be total_score is alway 0.

edit2. my expecting result is something like the following (may not exact)

Example Input:

Score? 91
91 - PASS
Score? 70
70 - PASS
Score? 69
69 - FAIL
Score? h
3 score entered, 2 pass
average score is 76.67

Source Code:

#include<stdio.h> 
#include<stdlib.h>
#define PASSING_SCORE 70

int main()
{
    int next_score;
    int n;
    int score_count;
    int pass_count;
    int fail_count;
    int avg_score;
    int total_score;

    score_count = 0;
    pass_count = 0;
    fail_count = 0;
    total_score = 0;

    printf("Score?");
    n = scanf("%i",&next_score);

    while(n==1)
    {
        score_count = score_count + 1;  
        total_score = total_score + next_score;
        if (next_score >= PASSING_SCORE)    
        {
            printf("%i - PASS\n",next_score);
            pass_count = pass_count + 1;
        }
        else
        {
            printf("%i - FAIL\n",next_score);
            fail_count = fail_count + 1;
        }
        printf("Score?");
        n = scanf("%i",&next_score);
    }

    if (score_count == 0)
        avg_score = 0;
    else
        avg_score = total_score/score_count;

    printf("\n%i score entered, %i pass, %ifail.\n",
        score_count,pass_count,fail_count);
    printf("average score is %.2f\n",avg_score);
    return EXIT_SUCCESS;
}

Upvotes: 2

Views: 119

Answers (2)

Bill Lynch
Bill Lynch

Reputation: 81986

By changing two lines of code, I believe I have the correct output:

  1. Declare avg_score as a double.

    double avg_score;

  2. Cast total_score to a double when calculating avg_score so that we don't use integer division:

    if (score_count == 0)
    avg_score = 0;
else
    avg_score = (double) total_score/score_count;

Let's try running it with these fixes:

[8:59pm][wlynch@watermelon /tmp] ./foo
Score?91
91 - PASS
Score?70
70 - PASS
Score?69
69 - FAIL
Score?h

3 score entered, 2 pass, 1fail.
average score is 76.67

Upvotes: 1

quantdev
quantdev

Reputation: 23813

Look at your compiler warnings : avg_score is declared as an integer, but you print with %.2f.

You probably meant to declare it as a floating point number : double would work. Or print it as an integer with %d, I'm not sure what your code example is about.

EDIT:

To correctly compute your average (as commented by @Mike), you should cast one of the quotient operands to double :

avg_score = total_score/(double)score_count;

If not, you would get the integer quotient.

Upvotes: 5

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