Thread: Help with integer sum using for and while loops

I have an assignment that calls for a C program using a for loop AND a while loop that will receive an integer (called daNumba) and double it -- Using the integer the program will call the sumFor function and then the sumWhile function. These functions will both sum the values from daNumba to (daNumba * 2) ifdaNumba is positive. If daNumba is not positive it will add the values from (daNumba*2) to daNumba. Both functions will receive the value of daNumba and return a summed value. The only difference between the 2 functions is that sumFor will only use for loops and sumWhile will only use while loops. We are not to use arrays.

The program compiles without error. So far my while loop works for positive integers, but not with a negative integer (I have it commented out) I cannot get the for loop to work properly This is what I have so far -- I am stuck.... I am not looking for my work to be done, but to be pointed in a direction that will help me understand how to properly code my assignment.

Code:

  

#include<stdio.h>
#include<stdlib.h>
#include<math.h>


int main ()
{
        /*      Declare variables       */


   int daNumba, daNumba2, sumFor=0, sumWhile=0;


        /*      Display welcome message         */


   printf("\nWelcome to sumTimes2.\n");


        /*      Message indicating what the program will do     */


   printf("\nThis program will sum the integers between the one you enter and\n");
   printf("the integer that is twice that value.\n");


        /*      Ask the user to enter and receive an integer      */


   printf("\nPlease enter your integer: ", daNumba);
   scanf("%d", &daNumba);


          /*      sumWhile program      */

      sumWhile=daNumba;
      daNumba2=daNumba*2;
      while(daNumba<daNumba2)
      {
         sumWhile += daNumba;
          ++sumWhile;
          ++daNumba;




/*
        else if(daNumba>daNumba2)
          ++sumWhile;
          ++daNumba2;
*/
       }
       /*      sumFor program  */


       sumFor=daNumba;
       for(daNumba=sumFor; sumFor==daNumba2; ++sumFor)
       {
         if(daNumba>0)
           sumFor=daNumba;
         else if(daNumba<0)
           sumFor=daNumba;
           sumFor += daNumba+sumFor;
           daNumba++;
           sumFor++;


       }


        /*      Display test statistics         */
   printf("\nFor says the sum is %d\n", sumFor);
   printf("While says the sum is %d\n", sumWhile);


        /*      Display ending thank you message        */


   printf("\nThank you for using sumTimes2. Bye!\n\n");


        /*      Return 0 for the compiler       */


   return 0;
}

I suggest you look at what functions are. You have no functions in your program at all. Even though your assignment says to make a sumFor and sumWhile function you declared integers with those names:

Code:

int daNumba, daNumba2, sumFor=0, sumWhile=0;

Take a look at how to define main the correct way .

Plus it would look like you need to know how if/else works in C based on this:

Code:

else if(daNumba>daNumba2)
          ++sumWhile;
          ++daNumba2;

and this:

Code:

 else if(daNumba<0)
           sumFor=daNumba;
           sumFor += daNumba+sumFor;
           daNumba++;
           sumFor++;

Just because it is indented does not mean it is the same block. For example, you would need opening and closing brackets like so:

Code:

 else if(daNumba<0)
{
           sumFor=daNumba;
           sumFor += daNumba+sumFor;
           daNumba++;
           sumFor++;
}

Take a look at our if tutorial .

Once you have read those and make an honest effort, repost your code and we will help. Just throwing together garbage and hoping someone will write the program for you does not count as effort on your part.

I did, read the tutorials on functions. That will give you a good start. As will the tutorial on using if statements in C. Also you edited your post to make your original request seem more earnest.

The skeleton of your program based on the assignment would be along the lines of:

Code:

//include files

int sumFor(int num);
int sumWhile(int num);

int main(void)
{
     //declare your variables
     int input, sumForReturn, sumWhileReturn;
     
      //get user input 
     //TODO: your code here
     
     sumForReturn = sumFor(input);
     sumWhileReturn = sumWhile(input);

     //output the results
     //TODO: your code here

     return 0;
}
int sumFor(int num)
{
     //TODO: your code here
}
int sumWhile(int num)
{
    //TODO: your code here
}

I was editing my last post when you responded. Take a look at the tutorials I linked to and the skeleton layout I provided. It should put you on the right track.

Try this: how to define main

Originally Posted by kcraiguejr

This is something I must be confused about. int main (void) means it takes no arguments right? Aren't I giving the function an argument by inputting an integer to be doubled and summed?

Your functions that you are calling are taking an argument, hence their prototypes (declarations) that I laid out in the skeleton example. However, you are not using the arguments that are supplied to main from the OS, hence that function should have it's parameter list as void.