Why is my program not giving correct output?

Question

Where is it logically wrong? I don't find it incorrect but the output it gives is just 1. It should give all the Armstrong number from 1 to 500.

     #include<stdio.h>
     #include<conio.h>
     void main()
         {
         clrscr();
         int a,b,c=0 ,d,i=1;
         while(i<=500)
             {
             b=i;
             while(b>0)
                 {
                 a=b%10;
                 c=(a*a*a)+c;
                 b=b/10;
                 }
             if(c==i)
    `            printf("%d",i);
             i++;
             }
          getch();
          }

First, `void main()` should give a warning, which compiler are you using? second `conio.h` is not a standard header and `getch()` is not a standard function, also `getch()` is not needed in your program, it's needed in your environment, what does that tell you about your environment? — Iharob Al Asimi, Jul 04 '15 at 18:33
can someone help in findind where the logic or format of the programme is incorrect — anindya, Jul 04 '15 at 18:33
Use printf statement as much as possible and find where you are missing your logic if you dont know how to use a debugger. — Steephen, Jul 04 '15 at 18:36
`1` is the only time that `c == i`, try printing `c`. Also, put a space (or other delimiter) after the number inn your `printf`, otherwise you won't know where one number ends and the next starts, `printf("%d ", i);`. Do you know that `d` is not used? — cdarke, Jul 04 '15 at 18:51
there are only 2 valid (and one optional) way to declare main() all methods return 'int'. strongly compile with all warnings enabled (for gcc, at a minimum use, "-Wall -Wextra -pedantic" ) — user3629249, Jul 04 '15 at 20:15

score 5 · Answer 1 · edited May 23 '17 at 12:21

5

You need to initialize c before the inner loop:

 while(i<=500)
 {
     b=i;
     c=0;    /* reset 'c' */
     while(b>0)
     {
        a=b%10;
        c=(a*a*a)+c;
        b=b/10;
     }
}

You are using non-standard signature for main(). See: What should main() return in C and C++?

edited May 23 '17 at 12:21

Community

1
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answered Jul 04 '15 at 18:37

P.P

117,907
20
175
238

but I have initialize it in the beginning – anindya Jul 04 '15 at 18:40
@anindya You have to initialize it every time you are checking a new number. – Gaurav Sehgal Jul 04 '15 at 18:41
Yes. But that's not enough. Once `c` becomes something, you need to reset it to `0` before finding the next Armstrong number. Otherwise, you will keep adding to previous `c` which is not going to produce correct result. – P.P Jul 04 '15 at 18:43
then it does not add it to the previous sum of cube of a number – anindya Jul 04 '15 at 18:43
you are right igot it – anindya Jul 04 '15 at 18:44

score 0 · Answer 2 · answered Jul 04 '15 at 20:27

if you run the following code

you will see why there is only one output.

Note: correct declaration of main()

Note: using common functions rather than the proprietary conio.h

Note: uses simple 'for' statement rather than 'while' and increment of 'i'

#include <stdio.h>
#include <stdlib.h>
//#include<conio.h>

int main()
{
    //clrscr();
    int a;
    int b;
    int c=0;
    int i=1;

    for( ; i<=500; i++ )
    {
        b=i;

        while(b>0)
        {
            a=b%10;
            c=(a*a*a)+c;
            b=b/10;
        }

        printf( "a=%d. b=%d, c=%d\n", a,b,c);
        if(c==i)
            printf("%d\n",i);
    } // end for

    //getch();
    getchar();
    return(0);
} // end function main

Why is my program not giving correct output?

2 Answers2