c file all i'm getting is an infinite loop

Question

Can anyone help me out with the following c program? This is only my second program in c so I have no clue what I'm doing.

I'm trying to create a program in c to read a file "input.txt" and give students' math scores in asterisks based on a student's percent of correct answers

all I'm coming up with is an infinite loop of

+:*

-:*

*:*

/:*

input.txt would be similar to below

---

1 number of students

Karla students name

8 10 addition score decided by 8/10

50 80 subtraction score decided by 50/80

30 60 multiplication score decided by 30/60

2 5 division score decided by 2/5

---

with a desired output of

Karla

+: * * * * * * * *

-: * * * * * *

*: * * * * *

/: * * * *

---

my code

int num; 
char name; 
int sum;
int cur;
int i;
int avg; 

//call file
FILE*ifp=fopen("input.txt","r");
fscanf(ifp,"%d",&num);
for (i=0;i=num;i++){
        fscanf(ifp,"%c",&name);
        printf("%c",&name);
        for(sum=0;sum<=4;sum++){
            fscanf(ifp,"%d",&cur);
            scanf(cur,"%d %d")
            avg=%d/%d;
            if (sum==1)
                printf("+:");
            else if (sum==2)
                printf("-:");
            else if (sum==3)
                printf("*:");
            else if (sum==4)
                printf("/:");
            if (avg==1)
                printf("**********\n");
            else if (avg>=.9)
                printf("*********\n");
            else if (avg>=.8)
                printf("********\n");
            else if (avg>=.7)
                printf("*******\n");
            else if (avg>=.6)
                printf("******\n");
            else if (avg>=.5)
                printf("*****\n");
            else if (avg>=.4)
                printf("****\n");
            else if (avg>=.3)
                printf("***\n");
            else if (avg>=.2)
                printf("**\n");
            else if (avg>=.1)
                printf("*\n");
            else
                printf("\n");
        }
}
//close file
fclose(ifp);
return 0;

If anyone could help me out i would greatly appreciate it.

Answer 1

Consider the following For Loop:

for(i = 0, i < 10; i++)
{
   DoSomething();
}

The order that this executes is:

• run i = 0;
• run i < 10; if the result is "True" keep going. If the result is "False", leave the loop. Because i is 0 the first time around, and 0 is less than 10, the result is true. Keep going
• run DoSomething();
• run i++
• go back to "run i < 10; if the result is "True". . .

In your case, instead of checking if i is equal to num, you're actually assigning num to i. Because C treats 0 as "False" and anything else as "True", and because the "result" of i = 10 is 10 (see sidebar1) the computer evaluates i = 10 as "True" so the loop keep going

This is a pretty easy mistake to make in C because the compiler won't warn you about it. Static analysis tools like Lint will, but that's another story.

In Conclusion, you probably want "i = num" to be "i < num" or "i <= num" or some other conditional statement.

Sidebar1 This property allows you to chain assigns like a = b = c = 10. The result of c = 10 is 10 so that gets assigned to b. The result of b = 10 is 10 so that gets assigned to a.

Answer 2

Your infinite loop is because of your outer loop conditional: change for (i=0;i=num;i++) to for (i=0;i<num;i++)

As it is, you're just assigning i to num each time, hence the infinite loop.

EDIT: I should also point out that you have a syntax error on your lines

scanf(cur,"%d %d")
avg=%d/%d;

And that your avg variable is declared as an int, and as such you'll be performing integer division, which likely won't act as you expect; that is, you'll only get whole numbers, so your subsequent conditionals will be largely meaningless. You should make it into a float or double and cast one of your operands to be floating point