Why changing C++ affects program though the frequency that is counts is same in both cases

Question

1.00/5 (2 votes)

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C++

#include<stdio.h>
int main()
{
 /*to print the frequency of odd digits*/
   int i , n ,num,c=0;
   FILE *f1,*f2;
   printf("enter the no. of positive nos.\n");
   scanf("%d",&n);
   printf("enter the numbers:\n");
   f1=fopen("DATA.C","w");

   for(i=0;i<n;i++) 
   {
     scanf("%d",&num);
     putw(num,f1);
   }
   fclose(f1);

   f1=fopen("DATA.C","r"); 
   f2=fopen("ODD.C","w");

   while((num=getw(f1))!=EOF)
     if(num%2!=0)
       putw(num,f2);

   fclose(f2);
   
   printf("total frequency is::\n");

   if (num%2!=0) c++; 

   printf("%d",c);  
   return c;

if we put c++ below putw(num,f2) then the output is different but of same. why?
Above one correct

C++

#include<stdio.h>
int main()
{
   int i , n ,num,c=0;
   FILE *f1,*f2;
   printf("enter the no. of positive nos.\n");
   scanf("%d",&n);
   printf("enter the numbers:\n");

   f1=fopen("DATA.C","w");

   for(i=0;i<n;i++) {
     scanf("%d",&num); 
     putw(num,f1);
   } 

   fclose(f1);
   f1=fopen("DATA.C","r");
   f2=fopen("ODD.C","w");
   
   while((num=getw(f1))!=EOF)
     if(num%2!=0) 
        putw(num,f2);
     c++; 
     /*here is the fault*/
     fclose(f2);
    
     printf("total frequency is::\n");
     printf("%d",c);

     return c;

please check fault...

What I have tried:

I've tried running both sets of code

Posted 30-Nov-16 12:10pm

Member 12879870

Updated 8-Dec-16 22:37pm

Chris Maunder773K

v3

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CPallini 9-Dec-16 2:41am

I strongly doubt the first version is correct. Both pieces of your code looks flawed to me.

2 solutions

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Jochen Arndt · Answer 1 · 2016-11-30T21:27:00

Solution 1

Your code is was rather unreadable (thanks to Chris for editing; I tried it before answering here but failed).

But I guess the solution is

C++

while((num=getw(f1))!=EOF)
{
    if(num%2!=0) 
    {
        putw(num,f2);
        c++;
    }
}

while your code seems to be

C++

while((num=getw(f1))!=EOF)
    if(num%2!=0) 
        putw(num,f2);
c++;

Note that using proper indentation shows what is happening.

Posted 30-Nov-16 21:27pm

Jochen Arndt

Updated 8-Dec-16 20:51pm

v2

Comments

CPallini 9-Dec-16 2:38am

Thta's it. 5.

Jochen Arndt 9-Dec-16 2:53am

Thank you.

And thanks to Chris for editing. The code from the original question was unreadable and I failed to edit it.

Patrice T · Answer 2 · 2016-12-08T22:37:00

Not clear what is supposed to be c. if it is supposed to count the number of odd values, both codes are wrong.

You should learn to use the debugger as soon as possible. Rather than guessing what your code is doing, It is time to see your code executing and ensuring that it does what you expect.

Debugger - Wikipedia, the free encyclopedia[^]
Mastering Debugging in Visual Studio 2010 - A Beginner's Guide[^]

The debugger is here to show you what your code is doing and your task is to compare with what it should do.
There is no magic in the debugger, it don't find bugs, it just help you to. When the code don't do what is expected, you are close to a bug.