Help with looping

[john3j]

Hello,

I have the following code that works great:

#include <stdio.h>


int main(void)
{

int v=1;
int dist=1;
int i = (500 / 100);
float r = 0.05;
int val = 20;
float R = 0.05 * val;
float pwr_loss = (val * r) * (i * i);


    printf("\t  Voltage  \t  Distance  \t  Power Loss\n");
      printf("\t=============================================\n");

for (dist=1; dist<=9; dist++)

{
    printf("\t %7d \t %8d  \t %8f\n", v*100, val, pwr_loss);
    val = 10 + val;
    pwr_loss = (0.05 * val)*(i*i);
  }
    printf("\n\n");
    system("PAUSE");
  return 0;

}

How could I get it to run through the loop for a second time with

int i = (500 / 100);

changing to

int i = (500 / 200);

?

The output would give you the voltage, distance, and power loss with a voltage of 100 counting to 100 mile distance. It would then output the voltage, distance, and power loss with a voltage of 200 counting to 100 mile distance.

Any help would be greatly appreciated!

Thanks,
John

[rags_to_riches]

Here's a hint for you. For loops can start at any number, end at any number, and be incremented by numbers other than 1.

[oogabooga]

What do you expect i's value to be after i = 500 / 200 ?
It will be exactly 2, not 2.5 if that's what you were expecting.
It you need it to be 2.5, then try

float i = 500.0 / 200.0;

To do what you want you should first rewrite the code as a function that you call from main and give it whatever parameters you need (in particular you should pass in i).

You should also give i a better name.

[Click_here]

How could I get it to run through the loop for a second time...

Another for loop around that for loop.

for (dist=1; dist<=9; dist++)
{
   ...
}

Becomes

for (loop_counter=0; loop_counter<=2; loop_counter++)
{
    for (dist=1; dist<=9; dist++)
    {
        ...
    }


    i = ...;


}

Also note what oogabooga said about the data type.

[john3j]

I actually went through the code and rewrote it. Here is what I have:

/****************************************************************/
/*        CS263 Programming in C                                    */
/*        Assignment #3 Page 261                                    */
/*        Written by: John Strange                                */
/*        Date: 9/20/2012                                            */
/*                                                                */
/*                                                                */
/*   Compute the power loss in a transmission line with a       */
/*   resistance of 0.05 ohms/mile. Compute the power loss if    */
/*   500 kW of power is transmitted from a power generating     */
/*   station to cities at a distance of 20, 30, 40, 50,...,     */
/*   100 miles at 100 V and 200 V.                              */
/*                                                                */
/****************************************************************/
/*                                                                */
/*            dist = Distance                                     */
/*                                                                */
/*            page = Page number                                    */
/*                                                                */
/*            voltage = Voltage                                    */
/*                                                                */
/*            i = Current                                            */
/*                                                                */
/*            resist = Initial Resistance                            */
/*                                                                */
/*            R = Total Resistance                                 */
/*                                                                */
/*            pwrLoss = Power Loss                                */
/*                                                                */
/****************************************************************/

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

int main()
{

int dist = 20;
int page = 0;
int voltage;
float i;
float resist = 0.05;
float R;
float pwrLoss;


for(voltage = 100; voltage <= 200; voltage += 100)
{
    i = (500 / voltage);
page = page + 1;
printf("                                        ");
printf("                                    %d\n", page);
printf("\n                          Voltage: %d\n", voltage);
printf("                          ____________ \n");

for(dist = 20; dist <= 100; dist += 10)
{
    R = (resist * dist);
pwrLoss = (R * (i * i));
printf("\n            Distance                     Power Loss");
printf("\n            ________                     __________");
printf("\n               %d", dist);
printf("                        %8.2f\n", pwrLoss);

}

}
return 0;
}

Here is the output I get when I run it...



Voltage: 100
____________

Distance Power Loss
________ __________
20 25.00

Distance Power Loss
________ __________
30 37.50

Distance Power Loss
________ __________
40 50.00

Distance Power Loss
________ __________
50 62.50

Distance Power Loss
________ __________
60 75.00

Distance Power Loss
________ __________
70 87.50

Distance Power Loss
________ __________
80 100.00

Distance Power Loss
________ __________
90 112.50

Distance Power Loss
________ __________
100 125.00


Voltage: 200
____________

Distance Power Loss
________ __________
20 4.00

Distance Power Loss
________ __________
30 6.00

Distance Power Loss
________ __________
40 8.00

Distance Power Loss
________ __________
50 10.00

Distance Power Loss
________ __________
60 12.00

Distance Power Loss
________ __________
70 14.00

Distance Power Loss
________ __________
80 16.00

Distance Power Loss
________ __________
90 18.00

Distance Power Loss
________ __________
100 20.00

The problem is that it is still not computing properly when the voltage is 200. Can anyone help me figure out why?

Thanks,
John

Another for loop around that for loop.

for (dist=1; dist<=9; dist++)
{
   ...
}

Becomes

for (loop_counter=0; loop_counter<=2; loop_counter++)
{
    for (dist=1; dist<=9; dist++)
    {
        ...
    }


    i = ...;


}

Also note what oogabooga said about the data type.

[rags_to_riches]

I'm guessing you're running into integer division here, when voltage is 200:

i = (500 / voltage);

You've declared i as an integer, which means the decimal generated here is lost.

[john3j]

you are exactly right! thank you very much!